I think a lot of this depends on the provider's scheduling practices, and the amount of advanced scheduling you're doing.

I think there's a big difference between asking for a same-day appointment and hoping to get screening out of the way in a couple of hours, compared to trying to get screening and scheduling out of the way with more time to spare.

Part of it might be that you are somehow coming across as not being respectful of the provider's time. For some, it's just not worth the time and effort it takes to engage in extended scheduling discussions with people who will never follow through with a booking. Providing the requested and complete screening information is, for many, a sign that the gentleman (or lady!) is serious about booking, and is not wasting her time.

For me it is quite common to try to go through a screening process and never hear back at all. It's a pain, but hey, there are plenty of providers out there. They don't want your business? Fine. Find someone who does.

I totally understand people not wanting to dish over screening information if they have a limited window and are traveling to an area. I'm sure many other providers do as well.  If that is the case, the best way to go about it would be like this-
-send an appointment request via P411, as it makes you specify a date, time, incall/outcall. You could also initiate the message from your TER account.  
-send an email simply stating the situation.  

Example:
"Hi Priya! I am interested in seeing you (today or insert a date) in the evening for about 2 hours while I am visiting. Although I am travelling, I don't feel comfortable hosting from my hotel so I would like to see you for incall if it is somewhere in the DC/NOVA/BWI area (specify area if you want to). I am wondering if you can confirm you are available during that time, before I send over screening information?"

A message like that will get you a response from any reasonable person (at least in my opinion).  

What I will NOT do is get into extended discussions (3-4 emails back and forth) about my availability or whereabouts or specific activities/donations for said activities without screening.

Invest in P411.  You give your info once and get cleared through the site.  Then as you see ladies, they can give you okays on the site.  I have several okays there now and haven't had any issues with providers accepting this as a clearing for screening.  It also makes screening much faster in my opinion and just about all reputable providers are on there.

You have had wonderful suggestions...I agree that sending your info out there is ok to withhold prior to making sure the lady is even in theory open.  Certainly check P411 and their sites for the schedules posted...once you establish yes she is open...then send it.  I grow tired of experienced hobbyists waiting to be asked for details each step of the way.  I enjoy emails that explore then follow with the info needed to screen and verify.  

I understand that some providers only accept communication via their booking form, but others (myself included) will reply to an email or text enquiring availability for a specific date & time and then direct you to the booking form .  
Good luck  
Delightfully Yours,  
Sofia  
Your Authentic Brazilian Temptress  

Yes, you may be labeled a time waster, but in you need to know that nobody on here has your best interest in mind more than you do. If you decide to provide screening info which you say you have no problem doing than you just have to be prepared that you may have all the negative outcomes.
For example I gave screening info to a provider with multiple reviews. She first said she could not meet any days I listed. I inquired about something else and she told me fill out screening info to ask questions. I did agian, but did not hear back from her. That was fine, but about a month later I found out she had my info on a client list. For what purpose who knows? Triedto contact her about an appointment again and she said she was not seeing me. So she knew in the begining that she was not going to meet, but had me go through all that and then emailed me that she still had my info.  
So I had many simply not reply, but never had this happen before. It may be abnormal, but you have to be prepared for anything. I use references for screening as several providers are glad to be helpful. Only thing is you have to consider that you are now giving out some one else's info. I know not every is, but I try to be considerate and not give out someone's info to a unestablished or unvetted provider. Funny how a new provider wants all this info and they have 1 or no reviews.
Well like I said you have to be prepared to live with someone having the info you give them if its references, job info, or whatever else. I find that a good way to avoid this is to have a provider you know recommend some one. I have had several suggest friends and even make the introduction.  Not sure if they just passed my info on or vouched for me, but far easier process from request to meeting with no hang ups.
I think if you deal with a higher class of provider or just an honest one, you won't have these problems. Most legit ones, really want to screen to meet you. Can't get all the bad apples out of the bunch. Just hope this helpss you next time.

So most of the ladies have pretty much said what needs to be said. When it comes to the screening, I don't mind letting guys know days I have available if they contact me asking that. However, I will say there is nothing that agitates me more than getting a message that says "You available?" I get instantly hot headed and will do nothing more than send them my website. That message tells absolutely nothing and usually means are you free right now, which my website avidly states I don't do last minute requests. However, if the gentleman politely asks something like, "I'm in town next week and was curious if you would be available tues-thurs", I'm more than happy to suggest a specific day/time and work with their schedule. Once I get at least an inkling on whether or not I'll be able to accommodate them, then I ask for screening info. As per the other ladies, P411 is my preferred way of screening. It gives me all the same questions I ask on my site and lets me see the other ladies I need to contact for references. I do not accept "TER handle is abc123, I'm whitelisted there." Safety is number one for me and should be for anyone else who hobbies, but should closely be followed by fun and passion. You just have to find that happy middle ground. If I've learned anything, it's that you can't happily accommodate everyone but be accommodating to those that accommodate you Hopefully you find ladies that can help you with that!

Great screening. You just send your profile and ask about timing all in one swoop. No wasting your time, no wasting hers.

I agree with what a lot of the others have said here. IMO everyone is different in how they do things some girls have less patience and won't respond to anyone without having their screening information first. I, for example don't mind determining availability before going any further. I have a very busy personal life so I am not always available. If someone sends me an email just inquiring about my availability without providing any other info I will respond and if our schedules end up matching up, then proceed further.