Copied from a post by Pete Power on The Mokes Inc. Forum.
1st up you need new bearings or very clean good condition existing bearings. To clean a used bearing soak in Kero overnight and a quick squirt of Degreaser works well/ Make sure they are dry before greasing. I do not recommend using compressed air.
2nd and most important step is make sure you have a good quality HIGH TEMPERATURE BEARING GREASE. It should tell you on the container suitable for DISC brakes. A 500gm container will pack around 14 to 20 bearings.
I always find it hard to reuse bearings if they are 50,000kms + old for the cost of replacement and the amount of work involved doing them I reckon you may as well replace them. You are always left with spares this way. But budgets and other considerations will make your decision, ok enough dribble..
Gloves are a good idea but not necesary, clean grease though messy isnt dirty, a bit like KY! :)
With a good blob of grease in your palm and the large face of bearing on the underneath, you simply push the bearing edge into the grease. This forces the grease up between the rollers or balls.
You continue to do this in the same spot until the grease starts oozing out the top between the rollers.
Once you can see grease you slowly rotate the whole bearing while forcing the grease up. As the grease appears rotate bearing, easy eh. Continue until grease has been forced up all the way around, and go around again for good measure. Once your technique improves it only takes a short time to effectively pack a bearing.
Just smear off excess and fit bearing.
The original post on the Mokes Inc. Forum can be found here.
Thanks to Pete Power for the photos and text, and for allowing it to be reproduced here.