Me, I would do the epoxy primer, then apply the high build primer and block. Then when time come, do sealer, then topcoat. Like said, IF just a solid color, no metallic or whatever and IF you have it all mixed enough to do the entire car, and,.. IF you have same humidity and pressure, I say it can work. I much rather shoot the topcoat all at once.
Remember black is totally unforgiving!
