Go to Wal Mart and pick up a vacuum food sealer and some bags.
To easily back bearings, put a couple bearings in a bag with a good shmear of your favorite grease, run the sealer, and poof, the bearings will be perfectly packed with grease as the vacuum draws the perfect amount of grease through the bearing. The nice thing about this is that you can keep a few sealed, pre packed bearings in your spare parts box along for the ride... no mess, no tub of grease!
I like Mobil 1 Synthetic grease, will not emulsify when introduced to water, and lasts forever without breaking down. It is a high weight grease so even if a seal lip is torn, it wont come gooing out and fouling your shoes, or pads in my case!