Put a little rear axle lube on them when they get installed, then fill the hub as much as possible before installing it. (Or you can install the hub onto the spindle & fill it from the outside before installing the outer bearing cone & axles)
After you're finished fill the housing in normal fashion. Then when you get the truck running, drive the truck over into a shallow ditch to let the lube flow into each hub. Do this left & right sides. Then check & top off the lube level again. You're done!
