Painting - metal railing 50 years old

This is my second time to paint my metal porch railing. I painted it with Rustoleum and oil paint 8 years ago. (Don't know if that is a good amount of time that it lasted.) Before when I painted it was in horrendous condition and I sanded for a couple of weeks. It was mostly down to metal before I painted. This time the finish is mostly in tact except for a several places which are rusty and other places which the top coat is worn out and it is down to the Rustoleum. (The places that are rusty, this is not surface rust -- remember the age of the railing.)

Do I need to sand the entire railing to dull the finish? And do I put on Rustoleum only on the places which are down to metal or the Rustoleum layer or should I prime the whole railing?

I don't think I need to put Rustoleum over the black top coat if it is OK, am I right? If there is something I should use besides Rustoleum, perhaps you can suggest it.


I've got a Dremel tool this time, so it is going to be a lot more fun to sand the rust off.

thanks.
-cilla

It is a good practice to sand all the sound paint prior to painting [scuff sand is ok] Wherever there is rust, it is best to sand it down to clean metal [if possible :D]

Rustoleum rusty metal primer is a good choice but basically any solvent based rust inhibitive primer will work. You only need to prime the bare metal or rusty areas. If at all feasable - remove all the rust!