Have you heard of using wood glue? I stopped in a vintage vinyl store today and just learned of this process. I have not tried it but the guy says it is great. The idea is the wood glue and the vinyl do not stick to each other but the glue pulls out all the deep dirt in the grooves when it dries. Here are some links.
http://www.youtube.com/watch?v=Bm4bQVmV3Ok&feature=related
http://www.youtube.com/watch?v=Hq8jkEx7aiA&feature=related
http://www.youtube.com/watch?v=Bm4bQVmV3Ok&feature=related
http://www.youtube.com/watch?v=Hq8jkEx7aiA&feature=related