Kelsey-Hayes 4 piston brakes question

The psi difference between your typical compressor and a grease gun is a lot. I didn't know that either, I tried the air like you with no luck. Even if the grease is $20, it's still worth it imo. Yep messy, but a lot worse jobs out there.
Glad ya got them.
No, not .50 cents. A tube of Brand X all purpose cost $8.99 and it's almost empty after doing one caliper. Those K/H calipers hold a pretty hefty amount of grease. I can see now that bleeding them is gonna be fun. Not.
Made a hell of a mess too, but I guess better grease than DOT-3 all over everything. That stuff peels paint. Literally.