Just like the video above, I remove the outer shield on the bearing and I actually use a chain saw tip grease pump to push fresh grease through the bearing and hand pack the outside of it then reinstall that seal. I have run 3 bikes beyond 100,000 miles on the oe original bearings just doing that one time (usually within the first tire change or two). One of those bikes I rode over 256,000 miles with oe original bearings and it saw plenty of 145mph race duty/track duty in its 19 year life span but also was ridden through water above the footpegs, snow and salty roads too often as well, not to even mention the multiple times it was ridden for 1600 miles pretty much non stop heading to or from Bike week.
As far as the far outer dust seal, yes wipe it clean and the area behind it with every tire change, or anytime you have the wheel off just to keep the grit away more than anything.
Bearings themselves are pretty cheap though, and if you actually pulled the seal of both sides you would see they don't use much grease in them.
I see bikes all the time with sub 20k on them with rusty bearings or completely dry ones that you can feel are "gritty". Many of those are the cleanest bikes in the world and those cleaners can be harsh and dissolve the grease, or pressure washed or even a concentrated extended stream out of the spray nozzle of your hose will likely force some moisture into the bearing past that seal.
