How to Fix Streaks in Decoupage Glue Lightly sand the streaks with 400 grit sandpaper. This will not destroy the finish, but just polish the clear coat. ... Don't use decoupage glue as a top coat. ... Apply several thin coats, rather than one thick coat. ... Always use a matte finish. ... Use a foam brush instead of a bristled brush. Oct 2, 2019