Getting the head temp up as close to 180F as you can will help immensely. Also, as hamz suggested, back your glowplug off 1/4 turn from tight. This will allow some compression to get out. However, your more than likely not fighting compression but rather mechanical fit.
Make sure you put a couple drops of after run oil down the glow plug hole before you try.
Try forcing it over by hand by twisting the flywheel, but don't get it over the top too far. If you have it just over TDC, then the inertia you get when you pull the starter will help get it over the top again.
If it's that tight, you really need to get it up to 200F. Should help.