I sprayed on a guide coat 1 day after I sprayed a fresh coat of white epoxy and started blocking. I am using 120 (thought 80 would remove too much epoxy). It seems like I am having to sand quite a bit to get the guide coat off and the epoxy has a little bit of a "dirty" look to it after I hit it with compressed air. Is this normal for 12o and a light coat of spray-on guide coat. It's my first time blocking....any other tips? Thanks.