My electrolycist wants my whiskers to be 1/8 to 1/4 inch (5-10 mm if my internal conversions are working correctly). This requires three days without shaving. Which is terrible. I felt wretched when I went in the first time, having let my full face grow for that length of time. Then I discovered how little she was able to treat at a time, so subsequent appointments have been easier. For example, you could let a square inch under your chin grow (barely noticeable) and shave the rest and probably be fine for a one or two hour session. I'd suggest calling your electrolycist and seeing what she has to say about how much to leave unshaven.
*hug*
It'll be worth it, though, to be done shaving in the long run. 🙂