I am just curious, why did you not get a two stage air compressor? My understanding is that they are much more efficient, as in a lot more air cfm for the same amount of electricity to run it.
I am just a hobbyist, and I just do a little painting. I recently got a HVLP spray gun, that according to the spec sheet, uses more air than my compressor can put out. My compressor, an old 3 HP, single stage, with a 20 gallon tank. I had an extra 20 gallon tank given to me.
When using air tools with both tanks, the time to make the compressor turn on is about doubled. The time to fill both tanks is more than doubled. When I am working in the carport, away from the garage, I put the second tank close to my work, so I do not have a restriction of 100 plus feet of hose, and that helps maintain a higher pressure at the air tool. Both tanks are running at the same pressure. Because the inlet and outlet are separated on the second tank, it does trap a lot of water.
When I am painting with the HVLP gun, I run the second tank off the regulated pressure on the air compressor, at about 40 PSI. I drop the pressure again at the gun. When the air pressure is dropped from 90 to 120 in the air compressor to 40 PSI, in the second tank, it expands a lot, and it also drops temperature. When painting with this set up, the compressor runs maybe 25 or 30 % of the time. I have not yet had any water make it past the second tank.
That is how I use my second tank. You might be able to get some information out of what I do, or maybe not, but I hope it helps you.