That's essentially what I was going to write. I'll change a few words.
======================== I'd first remove the covers and hose the dirt and mold out of the condenser and evaporator, and clean out the pan that holds it all together.
The cold coil that faces indoors, absorbs water from the air. Sometimes they drain into the pan via a rubber tube.
Drill a drain hole in the floorpan toward the back of the unit. If the evaporator drains through a rubber hose, drill a hole to allow the hose to drain through the metal tray.
If the paper schematic is tucked inside remove it first, and don't soap or spray the electricals.
You can buy special condensor coil cleaner which is quite strong. I've had good luck with Simple Green. Actually, simple green is really excellent coil cleaner.
Put it on a table with the drain hole hanging over the edge and a bucket. A couple slats over a laundry sink or sump pump is much better. block up the other corner slightly, and just run the AC.
Normally the condensed water from indoors collects in the meetal tray, and the ring around the fan slings it onto the hot tubes to help cool them. With your modification, the water drains into yoru bucket or drain.
You could pour a little water in with the cover off to be sure it drains, without having to run it opened.
When you have it apart and are playing with it, don't turn it off and then back on quickly. Like an air compressor they don't start easily against pressure. I cleaned mine a few days ago, and tested it with a 3750W generator. The normal starting surge read about 10A, but when I turned it off and back on the ammeter read 25A and it loaded down the genny and wouldn't run.
(Actually, very well written commentary, thanks. I have modified both AC in my trailer to drain, and not to spray the condensor. It's usually so humid here (Rochester, NY) that the spray only collects dust.