...apart from the respirator mask advice, which I will not repeat ( have one rated for this stuff from the Home Depot, and I paint outdoors in the back yard), here is my experience with the Spraymaxx 2K clear glamour paint, which I have now used on maybe 7 -10 frames as the final step.
It seems to cover all paints equally well. I have used it over both enamel and lacquer, with equally impressive results. I've only been using it for maybe 5 yers now, so I can't speak to whether there might be some longer term problems with using it over lacquer...but thus far it has been a magnificent final finish both for looks and durability. You do have to make certain to mix it very well before you start spraying...the full two minutes of shaking and another two after puncturing the hardener compartment. The spray can and nozzle are pretty high quality, and if there is anything you need to watch out for, it is to get a good saturated coat on the surface of your bike tubing (without runs), or you will probably end up with a little orange peel in the final surface. Which is not all that bad, given that this is a clear, so orange peel is less noticeable.
I have never done any surface prep to the underlying color coats, other than to apply the decals before the final clear with Spraymaxx. One can seems to cover an average frame and fork nicely. There is some cautionary advice in the literature to apply it within a certain recoat window for the color coat...I think it's maybe 48 or 72 hours. But on my projects I have often gone longer than that because I like to let the color coats dry some before I apply the vinyl decals. When applied properly, the stuff goes on as a relatively thick paint layer. So I've never seen any point in trying to wet sand the undercoats smoother than they go on over the primer.
You do need to hit the thing with some kind of tack rag to get rid of any dust or surface lint a little before you do the final clear. And the can only has a useful pot life of about 24 hours. so I spray it all out in one go...fork first, then frame. Don't spray out the final few sloshes in the can as it goes empty, because there's some risk of losing the quality of the spray stream right at the end. I mask any polished chrome, and don't paint it with clear. I am fearful that there will be some adhesion problems down the road, and pealing clear coat is a problem I'd rather avoid.
Some examples:
