After adding extra time to your appt ???
How should the $$$ transaction take place?

It should take place at the time the arrangement for extra time is made and agreed on, and by you handing her the money. You're already in there, presumably you've given her the envelope. What else is there to be coy about?

This depends on when are you adding the extra time. I usually carry an extra envelope with an extra hour or two worth of $$. Then, if my appt. is going well and I want to extend my time, I simply ask the lady if she can stay longer. If so, I just give her the extra envelope. Most providers sites list their rates by hours. So, if you initially planned for two but think that you might want to extend it to three or four, then place that extra amount in the separate envelope beforehand as per the rate listed on the provider's site. This makes things the most comfortable as you would not have to ask how much nor would you have to count anything.  Hope this helps.

I had that in mind but was caught not prepared
with an extra env.