lilpaintchic, as you know, I am a big proponent of Gardz. I also agree that 2 (or, as you mention, sometimes 3) coats of Gardz are better than one. I have also found that if most of the dust is removed from the surface to be skimmed, a coat of Gardz will soak through and bond any dust that is left into the surface. I just have a question below.
I have been doing a lot of work for a contractor in a couple of Chicago hi rises. He does a lot of skim coating over the original heavy orange peel on the ceilings and walls when these condos were built. He begrudgingly agrees that Gardz is a good thing for sealing skim coats, but he does want a coat of 123 (or other white primer/sealer) on before he uses a bright light to look for defects as they are hard to find otherwise. I have to agree with him if I am going to just try and patch the defects.
I did finish one wall for him that got bright sunlight and needed to be very, very smooth and flat. I screwed it up using Easy Sand and asked him to fix it. He went over it with a pencil, then skim-patched with Blue Top mud that dries sort of yellow. I very gently sanded this down (I can sand this stuff with my hand) and put a coat of Gardz on it, let it dry, then skim coated the whole wall with Durabond 45, let dry, then sanded. I skimmed the whole wall instead of looking for defects as I always seem to find more defects while I am correcting the ones I have penciled as well as finding more once I am all done and starting to paint. I left the wall like this until he fabricated an opening where the wall was broken away so a prehung door could be installed, after which he finished skim coating with Easy Sand to blend it in with the rest of the wall. He primed it with 123 and I painted it 2 coats Regal Select. The only defects were where he had finished the wall with Easy Sand and primed it without giving me a chance to do my thing before finishing the wall. As the job had to be finished, we left it as it was.
My question for you (and anyone else here) is how do you find any defects in a skimmed (and possibly Gardzed) ceiling or wall without the visual advantage of a white surface - unless you thinly skim coat, then sand the whole surface?
Also, why do you advise against backrolling? I have found that paint going over a surface properly sealed with Gardz will not lose its moisture by it seeping into the wall, thus giving a longer time to work the paint before it starts to dry and tack up.
Other than that, I like your procedures detailed above.
futtyos