1. Don't worry about sanding through the pep file. It's gonna happen, it's natural. This part of the process is to show you how easy it is to patch a hole. Don't be afraid to sand, if you make a hole, then add some tape and rondo the back a bit, then continue sanding. It's a slow process I know, but it uses much less material than trying to plan that far ahead.
2. I only recommend it for molding helmets due to its expansion. You can use this on wearing pieces (I use it to back helmets with in my castings), however, I don't recommend this until you familiarize yourself with its use, expansion, curetimes, etc. Basically you'll get there but when you rush that's when accidents happen, and all the hard work you put into the piece goes out the window.
