I do not have the bearing buddy system. I have a grease fitting sticking straight out of each axel behind a rubber cap. I know to add grease about once per year. My question is how do you know when you added enough? I want it full, but too much will blow out the seal and cause bigger problems. any suggestions?

Sounds like you have the system that relieves the excess pressure and grease inside the axle. You can't overfill it. As long are you are not getting grease sprayed on the inside of the wheel as you tow, your seal should be OK.