4 speed ka-booom !

Well if you bought a tool, then use it. I suppose you might get away with the jelly and the tool. I have rebuild hundreds and hundreds of manual trannys. I never had a tool, and I would heave the jelly.
I used it one time, in about 1978. Never again. I still have the little jar in my workshop. Haven't found a use for it yet.
I have used many types of greases over the years. Common wheel bearing grease seems to work ok. It has a good tack to it, washes out fairly quickly, and is readily available. White grease works a little less well;it has less tack to it, so you have to be careful, but it washes out more quickly.