so, how should I paint the oil tank for my (almost) tiny house?

[jeff47]

1. Color doesn't matter. Usually it matches the house or otherwise camouflages the tank.

There is some danger in removing the rust too aggressively, in that you make the tank thinner.

I'd recommend only breaking off the loose rust, such as using a wire brush on it. The paint will cut off the supply of oxygen to the rusted area, and thus stop the rust from spreading.

As for what paint to use, you can use anything that's designed to stick to metal. Rustoleum is such a paint, and the folks at your local paint store can direct you to similar paints they carry.