Saw the neon heels diy at cheap chic obsession and had do to this! I'm so excited over the result. An old pair of shoes, which I wanted to sort out initially, has become a favorite item to wear.
I have used painters and scotch tape and my scotch tape didn't stick with the painters tape, so I wouldn't use it again. The painters tape was ok in usage, but like you see in the images it didn't stick that good on every part of the shoe. Next time I will try duct tape on the edges. But you can remove accidentally miss-sprayed areas with nail polish (easy on leather or smooth material, not that easy on rough material but still possible).
I found little stains on my shoes after spray painting. You can remove them with sand paper. Sand the part of the shoe with which you are unsatisfied and spray paint again. Maybe you will have to spray paint another white coat on that part, before the neon top coat. It depends on how much you take off of the paint with the sand paper. Be careful to not "work" a hole in your shoe and use 'fine' sand paper.
I'm very happy with the result, but the heels become dirty very fast! I will think about a glossy top coat or something like that, to protect the paint.