Everything you said is a good idea GCP.
I always try to remove as much surface rust as is practible.
I've always used a rust inhibitor, i've found Loctite 7503 is as good as any - i got it from my local motorfactors.
I then use a Zinc Primer (182 on the can?!), this gives some rust preventative qualities and good adhesion to clean metal, as well as providing a good base to any other paint that will then go on top.
I've got a few types of underseal in the shed, there's Tetrosyl, CarPlan, Hammerite, they come either in a spray can, or in a tin to be brushed on.
The spray gives a nice even finish, but not much depth (unless you use cans and cans of the stuff!!), the brush on stuff you can really plaster on and use to fill those little nooks and crannies where you can get build ups of road dirt that stay wet and cause all sorts of problems.
I can't say if any one is better than the other, but i do know they are a lot better than they used to be as they are more flexible when dry, so they don't tend to crack after time.
And don't forget to try and get good old 'WaxOyl' into those 'hard to get to' places
I hope this helps a little
good luck - and get some photos on soon!!!