Since you said 'Best Way'. The 'best' way is to remove the bearings and hand pack them and then put them back. That allows you to see if the seals are good and to inspect the other parts of the system. It also gives you a chance to inspect the bearings themselves to make sure they're not worn or beginning to wear.
Having said that, there are people who claim to have good luck using the EZ-Lube system and I don't doubt that. I would recommend removing and hand packing them the first time and then you could use the EZ-Lube for a couple of years.
Others will no doubt chime in.