My advise would be to get it up on axel stands, strip everything off the car then do as said above. Zinc primer, stone chip then body coloured Hammerite.
I'm not going for a concourse standard either, just so it looks clean and well kept, so I'm using Hammerite on everything rather than having it powdercaoted but have got a good result so far.
I did try to stone chip it with everything on but it just got everywhere and missed places which are coverd or hard to get at, which is where all the crap settles and starts to rust anyway!
Much easier to just take it off.
Only problem then is though, everythign looks old and crap so you end up painting and replacing EVERYTHING
