Krylon works good as it dires fast so multiple coats can be applied in a relativley short time frame. As to brush, roller or spray. one is as good as the other. You will not see brush or rolle rmarks or drips or runs from inside the tank. Same for flat, satin, semi-gloss or full gloss. its all gonna be hgh gloss when view inside the tank, but gloss or semi glopss is a lot better at getting salt etc off than flat paint is.
Same for latex, oil based or lacquar paints. Personal opinon, but Iwould only use latex on a acrylic tank, but for glass it makes no difference. And I am not so sure I would paint a acrylic anyhow as ammonia does affect acrylic and latex paint contains lots of ammonia, so it may cause problem later on.
I am more into those small 3 or 4" disposable rollers with foam roller covers, and a pint or quart of latex paint. No obnoxious fumes or overspray, it can if needed be painted while its in its spot and even if its setup and running.....As emperor11 stated, its gonna take more than a coat or two.