My 18 year old home has/had only primer on the metal bulkhead (to the basement from outside) and also on the metal basement window casings. There is light to moderate rusting in many spots. What is the best DIY approach to painting the bulkhead?
From what I read so far the safest approach seems to be to first sand/sc****/steel-wool as much spot rust as possible, then, to be safe, use primer that also bonds to rust (e.g. rustoleum), then paint with an oil-based enamel.

Is this the best approach?

Should I also sand the current primer coat areas that are not rusted?