I would like to know what I should use to paint inside my doors, kick pannel vents and inside the roof to prevent further rust corrosion.

I am not able to get at the little bit of surface surface rust that exists and it is almost impossible to get inside the vent holes where the kick pannels cover them and around the drip rails on the roof inside the car. Any solutions?

use the search engine....lots of posts here on rust removal,arresting.....slowing it down...etc. Look up por 15, rust bullet, zero rust, & rust converter.

Try eastwood
http://www.eastwoodco.com/jump.jsp?itemType=CATEGORY&itemID=372
I'm thinking of useing this Heavy Duty Anti Rust are one of the others in the link above.
http://www.eastwoodco.com/shopping/product/detailmain.jsp?itemID=1117&itemType=PRODUCT&RS=1&keyword=Rust+Encapsulator
Bob