honestly, you cant beat rust only delay it. with that said the only way i know to get rid of it for a short while is to weld new metal in to the panels that are the worst.
also using body filler after the new is welded sand and paint, it should work for a few years
2004 Lexus Es330, alive; 1999 Cherokee Sport
1998 Grand Cherokee, sold
1997 Grand Cherokee; Black and Gold, Limited 4.0....RIP 2005
to the good times and the bad, the family we have and lost, little brother 1988-2011