The #1 piece of advice I can give you is to get the paint I used. The paint store lady swore by this, and boy was she right! I guess she works there for a reason. I did nothing to this door but wipe it down with some light soap and water. No prep, no sanding, no priming. As a matter of fact, there is no priming needed for this paint.
I only bought a quart of it, and it has lasted through the back door, my barstools, and most of my bathroom cabinets. I still have about 1/4 left!
As you can see, I did not paint the interior. I taped off the deadbolt and door handle. For the cut in grooves, I used a cheapo sponge brush (see below). For the flat parts, I used a sponge roller. I SWEAR by sponge rollers. They give such a smooth finish, and there’s no marks left behind.
Just a little note…I did sand the chairs down. I did it before I knew about this paint, but I still would have (just not as much). I wouldn’t necessarily recommend never sanding. I just don’t think this paint needs much of it.
Good luck with the black doors, ladies!