Kelsey Hayes 4 piston calipers help

Ya, the tools that were invented back in the day, to get the job done, sure are nice to have.
Here's photo of the official Miller Special Tool that i also have.
Using air pressure to blow them out works, but only if the pistons haven't been stuck in their bores.
Then you need to be very carefull that they don't become exploding missels off the shop walls.