I usually caulk before I spray the first coat of primer. If you're applying a second of primer you can just caulk in between coats. I like to prime the caulk to seal it in, but even if you caulked after priming it's fine. Yes, High Hide White is the base color for this enamel before tint is added. The base color was Extra White before, but they changed it to High Hide White, which is slightly different. The base color is a bright white. I've sprayed cabinets with only the base color before, but most of my customers go with a tinted white. I've used Snowbound a lot.