I used to use model master paints. When I first started I bought like 50 of those little bottles. Less than a year later I had to throw most of them out. Its good paint, but those little bottles are garbage. The seals are horrible and the paint dries up or gets all crusty around the lid and the flakes fall into the paint, or the lids just get welded to the bottle, etc... Just horrible.
Paintjob is coming along nicely. For a sealer I recommend either Testors dullcote or an acrylic matte varnish for the airbrush. I rarely use gloss and I haven't found one that dries clear. They are all milky, especially if you put on thick or multiple coats. Heck even dullcote gets a bit of a shine if you put it on too heavy.