How do you clean your bottom where the boat sits on the bunks? If you do how do you raise boat off trailer?

Jack the entire boat/trailer up in the air 6 inches.

Place 3 supports under the boat, keel, and back two corners...
...made out of SOLID cinder blocks and 2" thick wood between boat and cinder blocks.

Then lower the trailer away from the boat.

Reverse process when done.

You can also try. First lower the tongue jack as low as it can thus raising the transon. Place wood blocks under transom. Raise tongue then all the way up and block the front. Then bring trailer jack back down.

Another option, boat to a local marina with rack storage and see if they will put the boat on a work rack. It will likely be less $ and for sure less hassle and safer.