If you're going for the temporary fix, then personally I'd get in there with a Dremel type tool first, preferably one with an flexible head attachment so that you can get better access to the difficult to reach areas. Remove as much as corrosion as possible, then treat liberally with a chemical based rust converter and leave it to soak in over night, before coating the whole area with an epoxy primer or zinc based primer, followed by a suitable top coat then soak with waxoyl or similar as suggested above. My door skins and door bottoms have been kept alive using this method for the past eight years now, and they'll probably last another winter before the inevitable reskinning too.
The issue is that rust inside the door bottoms is fuelled by rain water and condensation running down the inside of the door skin. If you can keep this moisture away from the corrosion, then you'll keep the corrosion at bay for quite some time. The other issue is to make sure that the drain holes in the bottom of each door are clear so that any water can escape, especially if you've been splashing paint and waxoyl about that might have blocked them off.
Edited by AVV IT, 19 May 2013 - 01:17 PM.