A friend showed me a stock B4 diff with AE black grease and Schumacher white grease and the diff was shockingly free
, much like a Tamiya pinion diff ! And it was absolutely not slipping. The diff has had 15-20 runs through it when I tested it.
So I would say Schuey white grease all the way (less is best here) and AE graphite grease for the thrust bearing.