it depends on the girl, but yes the same tests apply.  never say you want to buy sex.  a real girl may try to get you nekkid first.  since a cop wants to chat about deals before your nekkid....etc

keep in mind if they aren't highly reviewed look for other clues that they're not LE.   like are they traveling.  if you google the names and numbers evidence should appear that they are doing this full time and not just LE.

also use the boards that's what they're for.  you mentioned you narrowed it down to 2-3.  have you posted for any 411 on them here or anywhere?  if people have been with them, even bad service they're probably real.

good luck and remember... plead the 5th