Is the problem that your homemade "plug" isn't working as well as you want? If that's the case you can clean the bore of the one that's out--re-install that piston and use opened up hose clamps to then contain those remaining pistons except for the next one to get removed. If the pistons are frozen in a partially extended position use a "C" clamp to force it/them back first. Watch where you place your fingers--air pressure can launch the piston out like a rocket. - Dave