if the engine is locked up and not rusted up on you, remove the engine from the plane, then remove the glow plug and the backplate. Then oil it up using fresh glow fuel or WD-40. Then use a hairdryer or a oven heated to 200 degrees. Get it warmed up good, say 10-15 minutes in the oven. Then using a pair of gloves to hold it, put on a prop and it ought to free up nicely.
Then finish flushing it out with WD-40 or glow fuel some more. You should be in business then.
The heat treatment works for the carb too.

I had recently done that same thing to a old Fox 45 engine that was basically new, it just sat in a box for a jillion years.
I cleaned it up and bench ran for a while since it was new, and now it is on a SPAD3D plane.
The engine runs just fine in any case.