The NR bearings are sealed and lubricated with a thick grease. This grease creates drag when you spin the bearing. There should be no grinding noise or gritty feel when you spin the bearing though, if this is the case then something is wrong.
You can either clean all the lube out (big pain in the ass) swish it around in some gas to loosen some of the grease and then get it out with a rag or just run the bearing as is. Since it is the snap ring bearing it is in the transmission and the trans fluid will break the grease down over time. I normally get the bulk of the grease out of the bearing, in a few hundred miles the rotation heat and transmission fluid will have removed all the grease.