paint with acrylics. As for sealants you have a couple options. I'm using this stuff called Shields All right now on my 29 gallon. It's kind of pricey but i like it. Kind of makes it look kind of plasticy but you can sprinkle sand on it while its drying to break up the shine of it. Can also seal with silicone. I did this on the 10 gallon and didn't like it too much. Silicone is very strong especially when you are smearing it around like that where you are using alot of it at once. Do it outside if you do.

I know exactly what you mean. I was constantly putting my build into the tank and taking it out as i was making it to get visuals. Staring at the tank also to try and get ideas on how to shape it. Been there, done that!