driveshaft balancing

My friends Comet had undercoating applied at the used car dealership and they sprayed half the driveshaft...He got 100 miles down the road, figured it out and spent 2 hours under the car parked on a curb chipping the crap off the driveshaft with a putty knife. When they balance it, my guy taped a large fender washer to it and spin balanced it. After a few adjustments, he tacked it on and painted it. No problems.