" I don't use the silly things, they are nothing more than a sales gimmick."
Worked well for me for 5 years full timing. Grab the outer edges of the tire and do a push pull for play and pump the grease while spinning the tire. Never a spec of grease passed the seals. I changed to Oil Bath last year and happy with that using US Made National Oil Bath seals.
When I pulled them apart to do the OB the bearings looked great but that's a given since I used AMZ/OIL full synthetic grease. ;)
Would I use the system on drum brakes? NO, but I will never own drum brakes again.