Sorry for the late reply,
The first cab I built I tried spraying but couldn't get a clean finish so I sanded back and rolled on (with a foam roller) oil based semi gloss paint.
The finish was o.k but not perfect and oil based takes a long time to dry giving it plenty of time to attract dust.
With this cab I used water based paint (touch dry in 10 minutes) with a foam roller and no gloss and am so happy with the result.
A deep flat color that really resembles the laminate of a real cabinet without the cost of vinyl wrapping it..
It might depend on what color you are after but the blue that I got a guy at a paint store to match (match my buttons) turned out great.!
My only error was not using a tinted undercoat causing me to give this thing 4 coats before I got a nice deep, flat finish.
Your plywood might be a little "thirsty" for paint, maybe 'a few' coats of undercoat with a light sand in between..?
As for build time it was a full weekend cutting and putting together, followed by another weekend painting. Then about two weeks on and off
transplanting the computer over, building brackets and wiring up the IPAC to get it complete.
Hope this helps, feel free to shout out with any other queries..