I am in Capital Region, NY and want to winterize my sprinkler system by myself.

I bought a Husky electric compressor: 20 gal, 4.3 SCFM @ 90PSI and tried once. I am having a couple of questions to ask for help:

(1) I blow out the air zone by zone. But even for one zone, not all the heads will pop up. Is the pressure too low ( I used 50 PSI max) or 20 gallon is still too small?.

(2) If there is still some water left (due to the size of compressor), will that be damaging?

(3) The air was used up quite soon, maybe 1 minute or 2. So I just reduce the psi to 0, wait for the compressor for 5 mins, then turn psi to 50 again. Is this method okay?

Thanks very much,