What wheels does the camels mini have ? Are there caps in the center of the mags or hubcaps if they're steelies ? Has there been a lot of wet weather there lately , does the camel drive through water regularly or is there a dog that constantly pees on the wheel ? What type of grease are you using and how are you putting it on the bearing (I normally use the grease on my palm and push the edge of the bearing down flat through it technique , someone else can probably explain it better) ? When was the wheel last balanced ?

You are sure it's the bearing by the way and not something else making the groaning noise , could it be brake related or is the old bearing damaged ? Can you grab another hub/upright from somewhere (you'de have a spare there surely) and try it with all the brakes and see if that fixes it . Is the nut grounding on something other than the bearing and leaving the bearing loose while still getting the right torque setting ?