Goat , you should be alright with the 4 day gas off period .
As K36 can be sanded & painted after a 2 hour cure time ( by PPG's P sheets ) IN the correct temperatures ! Faster in hot slower in cold .
All paints/ primers /primer sealers shrink , its just a norm for anything with a reduction & evaporation of solvents of the chemicals !
The main way to keep from seeing sand scratch swelling is cutting your body fillers with a fine grit 180 grit before priming ( eliminates sand scratch swelling /soaking , or what we Painters call falling in )
Other then that your Prep seems to be decent
Dont come here as often any more , just popped in and seen my name mentioned Thanks Shawn