My basic rule is to render out either individual frames or uncompressed AVI and only apply compression at the end of the editing process. Just like with movie film, a (compressed) copy of a (compressed) copy loses quality every time you process it. If you're out of cash from buying new Poser stuff and can't afford Animation Master, google "Dogwaffle". It has a free version that assembles an AVI from a sequence of TGA frames, and lets you paint a variety of artistic effects - fractal brushes particularly - frame by frame on to the footage, before rendering out to AVI. With sufficient tinkering, you can do some very basic compositing with this prog as well.