Go watch T. RICE wax his shit, he literally puts his board and bindings on the pavement, upside down, drips wax, spreads it and scrapes it super quick. It's not science, I don't think.
Bingo, a little wax residue/build-up is going to do far less damage (?) to your p-tex, then grinding every rail, box, tree etc.
Everyday Joe Blow, it's not an issue, other then not making it across some flat spots, but if you're a boardercrosser/slalom gate runner, then I might worry about it.