Disclaimer: When you try this at home and kill yourself, I will not be held liable. I do not recommend doing this, ever.
First, and most important, forget everything you know about safety and physics. Because you will need to hang the boat from the ceiling to make this work. Also, your back will be on the ground and against the wall, so forget about proper shooting techniques.
Then sand as much of the boat as you can get to with it on the trailer, to minimize time being under the boat while it's hanging.
Then suspend. Bolt an engine host (not a cherry picker, which is something G&E uses to service transformers on telephone polls, not lift motors) to the motor, one in front, one in back on the opposite side.
Jack up the front of the trailer. Then drill and screw in some hooks from the ceiling, and on the wood of the boat, as far forward in the boat as possible. Tie the hooks together using tow rope. Slowly lower the jack, you will probably need to make adjustments to the rope length to keep it level. Now the front is lifted.
Now, jack up the engine with the hoist. Careful. The boat should be suspended. Use your bad lower back to slide the trailer out from under it.
Place jacks and jack stands underneath intelligent spots in case the boat were to fall. Get under there and finish sanding. (This is the part you shouldn't do, becuase you may die.)
Fiberglass repairs, filler, and sand. I got rid of some ugly useless rivets.
Use epoxy prime and topcoat within 24 hours to avoid having to sand the primer. I finished with 80 on a DA, that's it. If you need to do some spots by hand, finish with at least 320.
Now, go outside and calm down your landlord who is yelling at you. Talking about air quality laws and not being able to spray there legally. Calm him down and assure him that you're only spraying primer. Get into a conversation with him and figure out when he'll be back the next day, so you can finish when he's not around.
Hose down the walls and the floor to lock down the dust. Then spray the top with your color of choice after your landlord leaves. No need to mask anything extra.
Let the top dry, but make sure to shoot the bottom within 24 hours of shooting epoxy. Mask, razor blade on the tape for round edges of the design. Shoot your second color.
Wait about 4 hours, peel the tape back at an extreme angle to prevent pulling up good paint.
Big thanks to KameleonGT for hooking it up with the paint at a sweet price!