Also it depends on what type of paint. A latex or acrylic might be OK , but a laquer or oil base that contains volitile solvents(and that's pretty much all of them) won't as the solvent fumes can find their way into the water and harm or kill your fish. I would go for the latex or a solvent free acrylic/ enamel and have the room well ventilated.
Just get an outdoor/latex semi gloss (I use Rust-oleum Painter's Touch flat black) and a 4" roller and tray. Apply a coat and reapply after it dries. It usually takes me about 3 hours to get 5 coats on and does a real nice job. I wouldn't be using a spray paint in the house, way too much mess and it will contaminate your tank!