Bodywork is real test of patience. Can I offer you a little advice? Your final blocking and painting steps will be easier if you spend more time on your metal work. Try to get the sheet metal as straight as possible before using filler. You can easily check your progress with a good steel straightedge. Depending upon how much time you have to complete the job, I have had very good results using Flat Black Rustolium enamel as a basic primer coat. I apply it in a thin coat, using a good quality paint brush. This way there is no masking, and it will actually sand better than spray can enamel provided you let it dry sufficiently. The Rusty Metal primer works well on trunks and inner wheel wells. This paint is fish oil based, holds up very well to weather, and does a good job of staying in place on older cars. If your worried about it working with your eventual top coat, just block most of it off and spray regular automotive primer over it.
Lots of people don’t like Rustolium, they claim it is incompatible with stronger solvent based automotive paint. The biggest drawback is the amount of time it takes to fully “cure”. This would never work for a body shop, but usually hobbiest work at a slower pace. And it will hold up to weather better than primer, in case you want to drive your car while you’re redoing it. Just my opinions ?♂
I saw your other post later, I guess I thought you were doing it yourself ?♂ It’s hard to get anyone to do a overall paint job on an older car, the regular body shops don’t want to get bogged down on a long term project. I hope this works out for you, I would only repeat what a previous person said, just make sure you are happy with the results ?
Bodywork completed, fixed every spec of rust with steel, Every dent located by block sanding, then stripped to bare metal, coated with etching primer, two coats of primer, and sealer. Paint will be later in summer or fall.