blockout hacks??

was wondering what people use to block out large areas. i know most suppliers sell blockout, but was wondering if someone had something just as good?

i had an area of an exposed screen kinda wash away when rinsing out after exposure so it's not just some pin holes. had purchased a bottle of blockout at some ridiculous price which sat in my ink locker for months without using and even covered and closed and stored properly dried into a big nothing but a loss.....lol.