New to the world of DIY. I'm giving a new life to my old furniture. I sanded, stained and now varnished it but the varnish have small bumps in it (might be air bubbles) which gives it a rugged texture... idk what's causing that and how to fix it. This is my first coat so I can fix it with another one maybe but I don't want to make the same mistake twice. I've sanded this thing for days and don't want to start over.