Simply use a Air Filter at the Gun. This is the cheapest and easiest way to go. It is not as effective as a larger more expensive systems, but works well if you change filters as directed. Each ball should last about a week of daily spraying. We sell them in bulk for Around $2 a piece!

Also featured here is the Desiccant Color Changing Disposable Filter

MotorGaurd (Best Bargain)
Double Pack - 4 Pieces Disposable Filters $15