KH brake help

Hello all,
I’m in the process of changing over my brakes to the KH disc brakes.
I have the completed setup but having a hard time getting the pistons out of the calipers. I tried air to no avail used grease got one piston out but can’t seem to get the other one out. I’ve tired to place a metal plate over the removed piston and the grease just keep squeezing grease out around the plate.
Also have the bleeders rusted and can’t get them to move. Don’t want to brake them off.
One more question I’m doing this on my 62 Valiant wagon what or do I need to do any changes like a portioning valve?
Any ideas or help would be greatly appreciated