Really, a little heat from a blow drier (or a heat gun that has a low setting) will really melt the stuff off pretty well and make it much easier. Too much heat can damage wood though- be careful and go slow.
If the grips are wood, remove them. Then use boiling water. Pour it over the bayonet. If the scabbard is metal, give it the same treatment. The metal will be so hot that it will dry itself. On scabbards made of leather or fiberglass, you must be careful as they are easy to damage.
Mineral Spirits works really with removing it. I soaked my mosin with orange glo degreaser and it MELTED that crap off. When my garand came in, I used mineral spirits and hoppes #9
Back when SKS's were shipped packed in the stuff we would put them under a heat lamp over night which helped run a bunch out. Then a parts washer if we had one, or cheap break cleaner.