Remove rust inside door panels?

You said it has surpace rust!!!! Go to a good (Maybe Ace Hardware) and get a qt. of OSPHO. Buy a $2 sprayer and spray inside the doors till it is all very WET. Let dry all day, next day spray again let sit maybe 5 minutes but NOT dry to neutralize the OPSHO and rinse very good! Best to dry it with air. I would get Rusteoluem (can) in there best you can. Great sealer and tough. Like said you can lay the doors flat, one end whatever. There are drain slots on the bottom of door sheetmetal.