Does it help to bleach the area to be treated about a week or so before a treatment to show which hairs are growing and which are not?
I don’t know if this will make it more clear as some hairs will still be coming out to just shed, i.e. they won’t be in anagen. You can shave with the same impact.
If you want, you can techncially wax before you start any treatments. That will guarantee that all hairs that come in after that are in the right phase.