I guess you could also then alternate between the stuck one and the others so that you can apply pressure both up and down on the stuck one and maybe rock it free?
Long time ago I put a 3x3 or 4x4 "wood" on top of the piston and used a sledgehammer on the other end of it. But, this one was not entirely stuck, so I could turn it a little, until it hit that stupid spot. So, when the piston stopped, I continued pulling the crank over in the same direction until it did not come anymore. Then hit the piston, then turned the crank that little I got, hit the piston again, and continued until it was loose. But, I had it moved the other way several times to get diesel fuel down so I got some lubrication before I continued.
It was after that episode a guy told me next time to use gun oil.