You want the water to be soapy.
How to remove paint from galvanised garage door.
Remove all stains from the doors as they may alter the color of the finished paint.
This will allow the paint to adhere more readily to the metal.
Homestrip p v remover would certainly be the safest way to remove it.
Clean the garage door s surface with a water based cleaner and a sponge.
Use lacquer thinner for especially thick layers of stubborn paint.
It removes paint from all surfaces plus its non toxic no fumes or skin burns and is just as effective as your normal run of the mill toxic products.
Sand the areas with medium grade sandpaper where the paint has been removed to lightly roughen the surface of the steel garage door.
Fill a bucket with the hot water and several drops of the dish detergent.
First you need to give the metal doors a really good scrub with soapy water and a clean cloth.
Rub it into the galvanised surface until the paint begins to thin.
Maybe screw some sheet metal to the wood sides of the door to prevent taking the paint off your wood too.
Thoroughly soak the sponge and wring out the excess water to make the sponge damp.
Rinse the excess paint with a wet cleaning cloth or sponge.
Dampen the cloth with white vinegar and scrub down the entire surface of the garage door.
I ve never stripped the paint off a garage door before but i d think that would be a good application for a pressure washer.
Dampen a rag with isopropyl alcohol rubbing alcohol if latex paint or acetone if an oil paint.
Here s the link to the projects page on home strip and there is a link to purchase in the tool store.
Then degrease the door with sugar soap and allow to dry.