no batteries in the camera at the moment, but i just used acrylic paint from the art store and brushed it on. i forgot to check the opacity of the pain, and the stuff i chose ended up being only semi-opaque (meaning partially see through) so i had to do like 5 coats.
last tank i did i just maksed off everything else and used spray paint, putting on about 3 coats.
stating the obvious, but you paint the outside of the tank, not the inside. i have actually seen that mistake happen before.
HTH