Nifty tool that works as well as hand packing.  You still end up getting greasy either way, but not as greasy.  I used with Valvoline VV614 Multi-Purpose Grease (for GM, Chrysler, European and Japanese Vehicles) in the 16 oz/1 lb "tub".  Just put it in the bottom, grease fitting is too slow.  Seemed to push out most of the old grease while pushing in the fresh.  Easy to store and simple to use.
Don't be afraid to put a foot on it.  I didn't try using a vise, but others have suggested it for the more difficult/thicker greases/dirtier bearings.  You may want to preclean the bearing or replace it it's really gunked up.
Remember to buy seals if you need them.
Pictures 1) Freshly pressed bearing 2)Side shot of pressed bearing 3)After removing bearing
Nifty tool that works as well as hand packing. You still end up getting greasy either way, but not as greasy. I used with Valvoline VV614 Multi-Purpose Grease (for GM, Chrysler, European and Japanese Vehicles) in the 16 oz/1 lb "tub". Just put it in the bottom, grease fitting is too slow. Seemed to push out most of the old grease while pushing in the fresh. Easy to store and simple to use. Don't be afraid to put a foot on it. I didn't try using a vise, but others have suggested it for the more difficult/thicker greases/dirtier bearings. You may want to preclean the bearing or replace it it's really gunked up. Remember to buy seals if you need them. Pictures 1) Freshly pressed bearing 2)Side shot of pressed bearing 3)After removing bearing