I have always serviced my own bearings when they need attention. My trailer has the grease fitting in the center of the spindle which allows the grease to go to the back of the hub and pushes the grease out the front which i think is one of the best setups. If that set up isn't on the trailer i pack the bearings and 1/2 of the dust cap. As far as how tight to tighten the nut on the spindle i take it all the way in snug tight to ensure the bearing seat good on the races with the new grease then back it off to the next slot to put the pin in.