Just to be clear --- in the spring i pull the brake drums to inspect the brakes at that time i also repack the bearings by hand. I use a high quality double lip grease seal then I use the EZ Lube to add a little grease during the summer.
On another note i have a utility trailer with no brakes and i just use the EZ Lube fittings because i can see the back side and after replacing the single lip seals with double lip ones i have never had a leak past the seal. I jack up the wheel and slowly add grease while turning the wheel. As i said this works for me others have had problems.