One thing that I've had mixed success with - but when this works, it works GREAT - are acrylic craft paints such as those sold at Walmart, Michaels, Hobby Lobby, etc. The range of colors is remarkable, the price (between .45 and $1) is hard to beat for something that will last you several kits, and they clean up with water. Where I've run into problems is in mixing them for brushing/airbrushing - I'm thinking that these things tend not to age well, and after a certain point there's just not much you can do with them. Like I said though, when they work, they are spectacular - I did a 1/144 WV-2 WarningStar in them some years ago, and the quality was equal to anything you could get from Testor's at literally ten times the price. Please let me note that isn't a bash at Testors, they put out a good product at a reasonable price. But when you build on a budget, ya gotta look for alternatives.