About the compressor. Well, the compressor will only reach it's maximum
output level while trying to fill a tank. My guess is you wouldn't get
enough usable pressure from it, at least not enough to spray for very
long.
Getting an air tank cheap... check with your air or welding supply shops.
One welding shop where I first bought my oxygen/acetylene torch setup
charged me to purchase the tanks outright. Now that I moved to NH, the
new place wouldn't refill those tanks for me, ... anyway, they gave me
new tanks filled with the gases (one oxygen, one acetylene) for "just
the cost of the gas in them". When I need them refilled, I just swap
them at their shop for cost of the gas every time. I think the oxygen
last time I swapped was about $20 something last summer. Maybe you can
find something like that?