On my car, the door frame pillars were unsightly due to the previous owner having picked any old black spray paint and painting over the surface, without doing any paint preps to make it look good. Although it is not easy to see in the photo, the original paint was glossy and the applied paint is a matte color. There are lines where you can see that the original paint was flaking off. So I embarked upon fixing this so it looked better and didn't bother me anymore. :)

NOTE: DISCLAIMER: I would like to note that this is not the procedure or paint that you can use for painting your car, in general. This is only the door frame pillars that are commonly a different paint and sheen than the rest of your car.

Supplies

Spray Paint (I used Black)

Sandpaper (I used 400 grit up to 2000 grit)

Masking Film

Tape (painters tape, which is low tack)

Rags for wiping dust off

Step 1: Masking

First thing I did was mask off the area around the pillars of my door frame. I masked everything that I did not want to scratch or get paint overspray on.

Make sure it does not cover any part of the car itself as you will see a line where you covered.

Step 2: Sanding

Next is to sand the surface that you will be painting.

This starts with the highest grit sandpaper that will remove any flaking or oxidation and make he surface smooth. In my case, I used 320-grit, then I sanded it with 400-grit and 600-grit so the scratches were fine enough that the spray paint would hide them.

I then wiped of any dust, making it ready for painting.

Step 3: Painting

I painted this with a Matte Black spray paint that I bought from Home Depot. The only "trick" I can advise on this is to have a lot of patience. Just spray in light, even passes, just a little, so you get some black on it. If you try and do it all in one go, you'll regret it as the paint can sag.

You want to let this dry fully. So if you have something else to do, this would be a good time to let your paint dry.

Step 4: In-between Coat Sanding

Once the first coat is dry, the next step is to lightly sand the surface.

The purpose of this is to create small scratches in the surface in order to enable a nice strong bond between the two coats of paint. Use a higher grit like 600 or 800.