You could also use Acrylic medium to thin out the pant instead of water or retarder to slow the drying time. Thicker pigments seem to require more psi. If you are outside and it's hot and dry your paint will dry out faster. If you want it to dry faster don't add much water, but then it will also dry in the nozzle faster. You could also use Acrylic medium to thin out the pant instead of water or retarder to slow the drying time.
Thicker pigments seem to require more psi.