If you open one door and then ring the bell of the second also locked door, and girl opens door in nighty, might be safe
For me, if girl starts at head, as basic training says, then you touch her hips and or thighs with both your hands. If legit place, she will politely move your hands and "thats that". If is other, then off to the races!
If afraid of police trap, best way is to no do thing that is not legal. No allowed to solicit sex work. A tip placed under your glasses on table before girl comes in will solve problem. No words needed.