Greasing the axles & wheel bearings
Greasing the axle is simple. They don't really need grease to function; it's just to keep the inner race of the bearing from sticking to it after time. So, spray the axle with cleaner, wipe clean, and then apply a thin layer of fresh grease. Any standard grease is fine. Bel Ray waterproof grease works for a lot of MC needs (and trailer and car and bicycle). If there's too much, it'll get scraped off. For streetbikes that live indoors this shouldn't be a major concern.
As for the wheel bearings - Don't. They are best left alone until replacement. Dirt or dual-sport bikes - sometimes maybe. But street bikes aren't often over the axles in water and dealing with perpetually dirty & dusty environments. You can't grease these bearings, anyway; they're sealed. You should probably put enough grease on the outside to discourage water from getting into the working surfaces. You couldn't get much of anything into the bearing proper, even if it were off the wheel.
Another thing that needs greasing are the spacers for the rear wheel. We have seen several which have visible wear, even though they are not supposed be a load-bearing item.
Also, pull the sprocket carrier and fill/pack the bearing with grease every time the wheel is off. The sprocket carrier bearing is actually more likely to fail than the wheel bearings, since it is -- seriously -- an OPEN bearing. This means the only thing keeping the grease from getting washed out when you ride in the wet is ... grease!