I'd go with Vinny's ratios, 1:1:1 isn't going to make it. The white pasty gunk could be Gum Arabic, which if I recall correctly, is used as a binder in watercolor paints. (Renarts, please correct me here if I'm wrong). I have had similar problems using tube watercolors as washes and abandoned them. I didn't use any vinegar and still got the white pasties, so I don't think it is the vinegar. After over 35 years of modeling, I have tried virtually every wash technique imaginable: Oil Paints, enamels, acrylics, watercolors, tempera, inks...you name it. What I use now are transparent airbrush pigments made by Golden Artist Colors. See; www.goldenpaints.com look under Airbrush Colors, Transparent. They make an entire range of these extremely fine pigmented transparent paints, which IMHO, make the best washes available. I use a combination of their "Shading Gray", (which looks black but isn't) and burnt sienna, diluted with water to produce a dark brownish-black wash. You will find these paints only at art supply stores. "Try it, you'll like it!" They help win shows for me!