I have used Krylon Fusion on PVC as well. I used PVC cleaner on the fittings and found it bonds with a smoother finish than sanding off the shiny finish. The PVC cleaner expands and softens the PVC and allows for a stronger bond. One thing I have learned is to use as directed when applying additional coats. If you wait more than 24 hrs the solvent in the paint that allows it to bond to the PVC will actually pull up the partially cured paint already on the piece. I believe the full cure time is one week and after that I have repainted pieces with no problem.