Another good way is to keep away from Testor Acrylics !!! There's so much color these days in a variety of paint and form that I can't see why bother with the crappy things. BUT, the little filter is a good thing to have for every kind of shooting... not absolutely necessary but a nice to have kind of thing... I don't have one though so I can't comment on their real addition to the process, I don't feel like I need to have one since I spray Tamiya Acrylics just a few time a year and never have problems with the paint. The only problems I had was with a "not well done" cleaning. So shame on me. It never happenned again.