There is this stuff called "skimstone". It actually is Portland cement, some silica fume and some sort of polymer admixture which allows it to stick to a lot of substrates. They sell it as a floor resurfacing treatment, but I (and others) have messed around with it in a variety of other applications and it seems to be a pretty good product. There are a couple of places to check it out skimstone.com and cemetics.com. I would certainly still do sanding or deglossing, and use an appropriate prime on melamine