Painting inside hood?

Hi all
It's me again.  That fly on the cyber wall.
Anyways, I'm constantly lurking around these
here parts. And have learned a lot.  I now
have 2 plant tanks out of 5. {I'm working on the
others}  Here is my question.
I want to paint the inside of the hoods white. Do I 
need to seal it or something?  Or just go get a can
of Rust-o-Leom and paint away??