Get yourself a good rust treatment to paint on any bits after you deal with them ,(if there is a lot best to get it cut out and new metal put in) ,i use one made by a company called Granville (blue liquid) then use an etch primer for any bare metal ,then primer over this ,on mine i then went over this with a flexible under body spray to help protect against stone chips ,then paint ,have a look on my resto thread ,may help you