Well yes, you have to sand the outside, but you also will use filler to level it out (fill, sand, repeat, fill sand, repeat). The outside will get sanded down flat at least 320 grit before the primer goes on.
The inside sanding is just to get it flat enough to glass in the reinforcing cloth reasonably flat.
In my experience this kit is about as good as fiberglass kits came, maybe Jet Model was a bit better, Yellow a bit behind but close. This is just stuff you have to do to build a fiberglass kit, nothing unusual. It all depends how good you want it to come out. I know one thing you can make it a hell of a lot better than the ARFs out there.
Last edited by mr_matt; 02-22-2018 at 02:52 PM.