Luke normally a standard water trap is fine for spraying. You need to make sure the filter unit is not to close to the compressor. Basically water traps work by allowing water droplets to fall into the trap, if they are to close to the compressor the air will be to warm and the water will not have condensed and be able to be trapped. Incorrect positioning of a water trap often causes problems (so does a horrid damp day where i swear my compressor pumps more water than air). The other common problem is not draining the tank at least once a day.