If you're just gonna spray floor polish out of it you can get a cheap air brush and canned propellent for less than $25.00
http://www.tcpglobal.com/airbrushdepot/8821x.aspx
If you're going for long term use ya need to educate yourself.
Buy the cheap one and play with it to see if you really want to invest in a good setup.
PS, as stated before, you can brush on Future Floor polish. It's self leveling.
I set the body on an up ended brick in a plastic bowl and pour it on. Of course I'm lazy.