Did you remove/replace the bearings?
If so, are the bearings in the wheel sealed?
If you did not remove the bearings, did you clean them in place?
If so, and they are not sealed bearings, they are probably now full of crud no matter how clean they might look on the outside.
Go read the manual. This is basic stuff.
You might as well just remove them and replace them with new sealed bearings. Then the only greasing you need to do is a light coating to prevent things from rusting.
I prefer waterproof wheel bearing grease.