Gardz question

Yes, and I've read a LOT about Gardz, and no one has ever mentioned using it for a topcoat sealer. This option isn't listed on the instruction sheet either. About 8 years ago I painted all our interior doors black. I didn't know what I was doing and only primed and painted them with who knows what kind of paint. For sure I would have primed with Kilz back then. By now they look awful with chipping paint. I plan to repaint them White starting with Gardz to seal in the black paint, but I can't see what's going to keep the new white paint from chipping off and showing the black paint through. I could use Polycrylic I suppose but I keep wondering how Gardz would work and if it would yellow. I might use Gardz, then white prime and then one coat of topcoat paint then Gardz again and then the last coat of topcoat. For sure I don't want to go through this process again in the future. I already painted one door (before I discovered Gardz) which I primed and painted with SW Proclassic and no sealer. It already has a chip on it with the black paint showing through. Thanks for your answer by the way.