Good question! You can fill dents with a patching compound. Your local hardware store or Amazon should carry one called Zinsser Ready Patch that works on metal and is for both exterior and interior use. Use a putty knife to put it on and press into the dents. Then let it dry and sand smooth.

How about laying off the roller marks to mimick the grain

Thank you!!

You will probably need at least 3 coats of a paint w/ primer built in, just because red is a really hard color to cover over and still have the new paint show as the correct color/tone. Personally I would probably do one coat of white primer and then the deep blue paint just so I'm starting with a clean slate color-wise.

Mine was metal and in really bad shape. But if you don't have bubbling of the paint like I did you don't have to strip it. You can just sand down smooth any little imperfections to get a smooth surface and paint right over the old paint.