Not that different than an outfit request or, if you already have met the provider, asking about an off-menu item.

Since the request is obviously explicit in nature, I'd be cautious about bringing up the activity with a provider that I have not already met or at least allowed to screen me thoroughly. Maybe first, just inquire if she takes special requests such as acting out a scenario or role play before actually sending a link to the clip.

At the end of a session with an escort wherein things have gone very well, bring it up to her as a suggestion for increasing the intensity on a future session with her. This can work especially well if and when she's given you evidence during the session that the act you want to do is ok with her. For instance, I was recently in a first-time encounter with a woman who responded very well to DATY, so much so that it was practically the main event during the 2 hours we were together. I've long had a fantasy about something related to that, and as we were getting dressed to leave, I sort of blurted it out to her to see if she was interested. She was, and not long after that, we had another session where we played it out.  

I hope this helps in some way.

More often than not, if you send that kind of request out there with a "link", it's doubtful that you will receive a response. From a provider's point of view - it appears either as a fantasy booking where you are typing with only one hand to her response or LE.  We don't know who is on the other side of the screen, so it is safer in the long run to not respond. Also, keep in mind that although some providers may be okay with a client speaking freely after screening is complete, some aren't and will decline your meeting if you attempt discussing anything explicit. Its best to ask what their comfort level for discussing particulars after screening. This is gives her the opportunity to set the boundary while preserving the possibility of meeting.  

IMO Its best to build up a rapport with someone you have seen before - this is the most likely scenario where she would be more comfortable communicating and curating a specific experience for you.

Also keep in mind that some porn uses special effects or multiple takes to get it "right."
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That scene where she manages to work a fire hydrant up her ass? Fake.  
That scene where she appears to take 5 gallons of cum shot on her face? Fake.
Any scene with me in it? Fake.
Etc.
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But I agree that there is some mind blowing crazy stuff out there! And I agree that it can't hurt to ask.