Care to go into more detail on how to?
Happy to:
Basically, you get a big ol' glob of grease around the wide end of the bearing, just like if you were packing it by hand. Seriously: more than you think you need would be good, but surround the open part of the races (you know what I mean, guys, English makes it sound more complicated than it is).
Put the bearing and its grease in the baggie.
Activate the Grease-O-Tron 5000 with the same technique you would use to save a chub of ground beef.
VIOLIN! You will see the grease get sucked through the rollers and out the small end, thereby efficiently and evenly packing your bearings.
At this point, you <open> the baggie to install the bearing, or you just keep it as-is, stored in a vacuum-sealed, plastic-lined pouch that is tougher than the box the bearing came in and drop the now-sealed unit into your spare parts box. It's pre-greased, protected from vibration damage, protected from rust, protected from dust and all-but-sterile, ready to use at the side of the road with your typical home-brewed care and preparation.
I don't know that there's really enough info to write a book on the whole Seal-A-Meal super-device, but the only one I own is in the garage. I use it for probably 5 or 6 really persnickety jobs that annoy me. I learned this technique from a column called "It Worked For Me" in either _Popular Mechanics_ or _Scientific Forklift_ or _Malapropism Unadulterated_ or one of those magazines, Circa 1980. I never forgot the tip, I never forgot the column name, but I can't find the stinkin magazine for the life of me.
BTW, I also have some pretty groovy tips for using your long-time wife's (or Ex-girlfriend's) colander and curling iron as well as testing the tensil-strength of Tupperware. I may even write an article called "Preparing Your Freezer To Do Your Dirty Hydraulic Work Without Rendering Your Fish Sticks Inedible."
Right now I just want to cuddle & spoon.