Is it inboard..outboard or stern drive power?? that has a bit to do with it..
If it is outboard drive just pull the engine with your engine hoist..there is a a built in picking eye under the hood just for this..
Get some blocking like 4x6 beams and lay them crossways of the boat..that is athwartship in marine lingo..let the boat come off the trailer onto the beams and when it is down off of the beams rotate it to one side and paint the bottom..then rotate it to the other side and paint the other side of the bottom..Once the bottom is done then block the boat upright and do your topsides...
Use old tires (no rims) to lay the boat on as that will support and not mar the hull..
Do the interior before you do the topsides so you are not working over freshly painted topsides..
Bout all I can think of for now...
I have tried most all of it and now do what is known to work..