Steve, about the best way I found to do the jambs is with the 3m ez edger machine/
you probably use it already, the one that just folds the edge of the tape over on itself. It works best with a transparent sealer, colored ones always seem to go in farther than the basecoat for some reason! The foam tape seems to leave a hard edge all the time no matter how you do it. Unless you consider taping it up so you can open and close the doors while spraying, but again this is going to leave darker edges around your doors unless you just avoid going in the jambs with the candy, Ive never had much luck painting them unless all together like your doing, and I was never totally happy with the edges in the jambs.
Spraying in California seems to be next to impossible at this point, and I feel your pain on the lack of support from jobbers, the big MSO shops have squeezed them so tight that even the local finishmaster stores are shutting down and consolidating locations.
Good luck with the job, Id love to see some pics as it progresses