I need to tile a new corner shower stall. I put Hardi waterproof backer board on the wall and used thinset to seal all my seams and screws, also used thinset for my transition seam between the drywall and backer board. I used a setting joint compound (not a pre mix drywall compound) to feather my seam from my drywall onto my backer board, also primed and painted it. I was going to put Redguard water sealer over my thinset joints and the backer board but I just found out you can't use Redguard over setting joint compound, primer, or paint. Can I just use Redguard on the backer board up to the painted compound, then find somekind of water sealer to put over the painted surface? There is backer board behind the compound, primer, and paint, I just needed to feather the compound onto the backer board over my transition to keep the wall level, it runs about 12 inches onto my backer board. In the pictures you'll see that the transition seam starts at the end of my shower base. Any ideas would be very useful, thanks...