I do not use the same wash for all projects, or pieces. For kit Chrome, I prefer enamel, cleaned right away, but sometimes that is too harsh to clean off of painted pieces. In those instances where I am going over paint, I like water based paints, and really enjoy the results that Ray demonstrated above with the kids water acrylics. Like many other aspects of modeling, there is more than one way to do it, but basically, it is just practice a lot and find what works for you.