Check out your local arts or crafts stores (~~firebomb~~ avoid Hobby Lobby). Artist grade paint is going to be superior quality for less money. You can also find Mulliput and Aves Apoxy at a lot of shops. Utrecht, Golden, and Liquitex are all good brands of acrylic paint. And usually shops that carry artist acrylics will also carry oil paints and inks. Windsor Newton and Gamblin are the most common, high quality oils. You can use these to make washes similar to Vallejo's weathering products. Pastels can be ground up to make powder for rust effects. You'll just need something to help bind the powder in place (I use acrylic gel medium).