If you did not do a good job of scraping off the old paint or there is chalking that you can t get to come off then you should first paint with a primer.
How to get paint off steel siding.
Make sure to use the power washer on the lowest setting it has.
In a few simple steps you will learn how to.
Wash the steel siding with trisodium phosphate tsp and use a pressure washer to rinse thoroughly.
The first step includes cleaning.
Set power washer to the lowest setting available.
Liquid dish soap will enhance water s ability to remove paint spots and is the next best option if water did not work to remove the stain.
Using too much pressure can dent your steel siding or damage the paint.
Oxiclean spray makes both a great laundry pre treatment product and a general household cleaning spray.
Step 1 clean the steel siding.
And then i would use the rust oleum top coat.
It also helps to peel away the previous paint on the steel siding leaving it neat and clean.
Use rubbing alcohol and a cloth to wipe the paint as much as you can.
But i would use the oil based rust oleum primer which by the way takes forever to dry.
This will help clean away all the dirt that accumulates on the steel siding.
You may have accidentally splattered some you may wish to recoat it with a different color or you may want to get rid of the paint altogether.
Use your pressure washer to get to all the cracks and crevices you could not reach with the brush.
That is how you can get the paint to adhere to steel siding.
For old dried up paint.
Apply liquid wax on a ball of steel wool and scrub the remaining paint.
I suggest thinning it with 1 part thinner to 10 parts water and scrubbing on the stain only after testing a small inconspicuous area.
For my paint drips i sprayed on oxiclean and waited for about 15 minutes then returned and rubbed it with a scrubber sponge.
Then scrub the solution into the aluminum siding until the stain is gone.
I had to use significant elbow grease not to some mention finger nail scraping for some of the larger stains.
Paint thinner or acetone is said to remove paint stains but may also dull dull the finish on your siding.
It will definitely remove the dirt but the paint as well.
To use it add a few drops liquid dish soap to water and mix until it s sudsy.