I filled the back and the neck with 2 layers of grain filler and then stained it. I thought I had sanded it properly with 320 grit sand-paper. Must have either not put enough grain filler or sanded it too far back in a few spots on the back. I am not too concerned with the splotchy colour, but don’t want those spots to be rough when I finish it. Should I try to sand it smooth now and restain the back or leave it and then smooth it out with the finishing coats. Planning on finishing it with a satin finish, not a gloss.