How fantastic! I can't wait to see the completed suit being worn. You wanted advice on cosplay? Only two rules: 1. Don't do an embarrassing face plant in the middle of a crowd and destroy the costume. 2. Pee before putting it on.:lol Ha, ha! Seriously, I agree that you needn't sand the grooves. they look fine. However, should you or anyone else have this problem, a company called Industrial Polymer Corp. makes a thin epoxy material that is "self leveling". That means that it is just thick enough to fill pits, grooves, etc., but runny enough to be relatively smooth upon curing. Think of a gravel road with a puddle on top. You don't have rough water on top of the gravel, it is smooth and level. It is a quick way to eliminate hard to sand areas, Another is to use thinned modeling putty and a bunch of wood coffee stir sticks cut to the size of the grooves. Just trowel the putty into the groove, wipe the excess off the adjacent surfaces and it should look much smoother. I only offer this tip for a future similar project by yourself or another member. As I said, this situation doesn't bug me, I agree with your decision to leave the texture. Nice work.