When i was mostly receiving outcall back then i would usually put the money in a pile under the phone (like half is under, but its clearly visible) on the night table. Most SPs would not touch it til it was done. The few that took it right away often turned to be more of a "transactional" meetup, less "warm and gfe if you prefer". If they would litterally count it right away it was even more of a bad sign.
But when i switched to incall (mostly) i now use envelopes too. Sometimes its a white blank envelope (cause my mother bough a box of them so we not short) but sometimes i use the one i get with my mastercard bill

(yes i still get it by post, don't judge me). Only difference is there is mastercard adress on it ... but otherwise no personal infos. I used to throw them in the recycle bin, but hey now i got a second use for them
At home i have a "fake book" like in the movies (and a few other items) where i store cash, and once i showed it to the person i received, let her open the book, i found it funny to watch her face. I 100% trust her so had no issue.
As for the counting, i do it like 5 times before putting the envelope in my pockets before heading to Montreal so i know its the right ammount.Only thing that may change is when i see someone in agency and have no idea how the extra is gonna cost (or if its offered). In that case they normally have no issue for me to pay it at the end. I mean lets say we discuss after im out of the shower, i would need to get up, pull out the wallet, go back to wash my hands again... i dunno, feel a bit weird. With indies its (usually) possible to set everything right away during booking.