How to Target leftover hair- can I draw on myself?

Hi, I’m finishing underarm GentleLase treatment (Im fitzpatrick skin type 1, dark brown/black hair), I probably only need 1 more for a while, its sparse.

In the past I stopped my leg treatments because of this issue, where there were few hairs left and I didn’t want my tech zapping the areas that are already hair free… but they don’t know where that is after we shave the day before treatment.

Is it common for anyone to like, maybe shave the day before/of treatment, then use like, a white pencil (or another color the laser can’t see?) to circle areas we want the technician to zap when we go in? OR is there another way to indicate areas we want done? I dont want laser wasted, plus I worry that if they did needlessly zap where its already hair free, it could mess with it and stimulate growth or who knows what.

My last underarm treatment with a new tech, she zapped the heck out of my underarm, so I know she def did areas that were hairless, she said she wanted to be agressive and “make SURE”. I told her to please only do where there’s the slight visible stubble, but she disagreed, and I dont want that happening again.

Yes. I’ve done this before with a white eyeliner pencil.