new primered exterior steel doors need paint

We installed 2 new 9 lite service doors in our garage building. They are steel with grey primer coat.

What type of paint should I use?

I think a small roller would be good for applying the paint ?

The one door faces north and the other one gets the full blast of the glorious A.M. sun.

Just worried that the paint might blister or peel.

What about the part of the door that touches the weather stripping when it closes ?

worry worry lol

What say you ?

TIA,
shirley