I use high temp, disk brake bearing grease.

Here's a pretty good video of bearing packing. I usually stick 2 fingers through the center and press and drag the rollers through the grease in the palm of my other hand.

The idea is to get the grease to ooze out of the gaps in the bearing cage.

http://www.youtube.com/watch?v=agxjGtmHV_4

__________________
-Evan


Benz Fleet:
1968 UNIMOG 404.114
1998 E300
2008 E63


Non-Benz Fleet:
1992 Aerostar
1993 MR2
2000 F250