Painting an already painted steel door?

I was on here all the time before I started painting this entire house.

Why didn't I ever hear anyone mention laying a door flat before? Yes, brush strokes sort of show up and I use quality stuff from SW.

Better late than never.

Except I will (one day) be painting 3 sliding doors. 2 are big.

I'll wait till then and ask how you get those off the rollers. (pocket doors)

Also, I had a heck of a time getting the doors lined back up on the hinges, alone. So now I know there's a trick to doing it.

If I ever look at another 1,430 sf house and say, "oh, no problem. I'll just update it by painting everything and striping wallpaper" I hope somebody just shoots me!"

Laying doors flat to paint is okay(?) if you have one or two doors. I painted six doors, both sides, last night. One of them needed two coats both sides. In an office, where would I have laid them? On six sets of sawhorses? I couldn't have done both sides if they weren't hanging, not in one night. In all my years I've only painted a couple of doors flat, but for none of the conveniences or necessities mentioned. Not trying to belabor a point, but don't want an inexperienced HO to think it's necessary or even a better way, it's not.
Over applied paint will run and sag on a hanging door, but it will also puddle on a flat door. Properly applied, the paint will hang and level out on a hanging door.
A flat door is a greater dust magnet than a hanging door.
Working over a flat door has a greater risk of a drip from the brush hitting a finished area and getting missed or having to be brushed out creating a mar.
And the amount of handling involved in hanging a heavy door with soft paint could necessitate a possible recoating after hanging. And if you get deep fingerprint impressions on a sheen coat, good luck.
It's not worth it.

You could literally fill a book with stories of general contractoritis. Where doors do require removal, cabinets, I have a good one. I did a twelve door built in for a gc. I wanted to prime the doors and sand them when they came, but he told me it was a waste of time, in a tone like I'm stupid, because he still had to fit them and an edge or two might need shaving. Besides, he says, the doors will then be hanging and it will be easier. I told him touching up a shaved edge is not a big deal and that shouldn't stop me from getting that bigger phase done. Then I told him that cabinet doors don't get painted hanging anyway. He says what are you talking about, you always paint cabinet doors on. I said you don't know what you're talking about, and from there it escalated into a shouting match. It had nothing to do with the job, as he wasn't even there during that period. It had everything to do with his knowledge of my trade being challenged. He ended up telling me to do it however I wanted, in a tone like he was pacifying me and was ready to tell me I told you so when I "screwed up". Yet try giving any one of those guys some simple tips on how you can give them a better paint job, and watch the doors blow off. Example: Take a piece of sandpaper and knock the furry edge off of cuts before you join them. Or, knock the furry edges off of hinge cutouts before installing the hinges. Or, sand your overly excessive drywall patches before you install a cabinet body over them and force me to do all that sanding right up against a cherry cabinet panel. A little forethought, and some respect for my trade, that's all I ask.