A lot depends on how much of a hurry you are in. If no hurry, repeated soaking alternating with heat cycles may free the piston. with no damage. As for the “grease gun” this works best if the piston is stuck up near the top of the cylinder where no ports are open. One will need a custom made fitting… grease gun Zirk into a spark plug body.
With the slow soak method it’s helpful if the spark plug hole is inline with the cylinder, thus allowing inscrtion of a wood dowel and tapping the piston to get movement.
Your favorite “soak” penetrant oil or ATF fluid.
Joe B
