The rust oleum product shown recommends an oil based top coat which should not be used when repainting a metal garage door.
How to fix rust on bottom of garage door.
Dip an old cloth in white vinegar do not use cider or spiced vinegar and wipe the rusted areas with a steel wool pad.
First clean the entire door with the water and dishwashing liquid.
Cleaning steel and aluminum doors.
An alternate product might be corroseal which is a rust converter and latex primer in one which can then be topcoated with a latex paint.
The vinegar reacts with the rust and dissolves it.
Soak the cloth in white vinegar and wipe all rusted areas.
In this video i focus on door bottom rust repair and will be showing you how to remove and replace a lower door skin on a car or truck.
Clean the bottom panel of the garage door with warm water and a grease fighting dish washing liquid.
How to fix a rusting bottom panel on a garage door.
Close the garage door.
Rinse and allow to dry.
Rinse thoroughly and let dry.
Dip a cloth into white vinegar and wipe the rusty area.