My suggestion would be to take the boat to a marine and have the bottom painted for the first time. This way you know the waterline will be straight and in the right place. I have gotten several boats on and off trailers, none as large as 23', but here is the process I used. Start and the back and find secure spots that are behind or to the side of the trailer. Jack the boat off the back of the trailer and block up. Now the boat should be support in the back by the blocks or jack stands and in the front by the trailer. To get the rest of the boat off the trailer you will need to find a secure spot in the front that will allow you to jack up the boat. Jack up and block the front. Now the boat should be completely off the trailer. You probably could paint the bottom of the boat just the way it is. If you want to get the trailer out from under the boat the you will need to go through a process of pulling the trailer forward until one of is cross members meets the blocks or jack stand you have holding up the front of the boat, block up behind the cross member and then remove the blocks or jack stand from infront of the cross member. Continue this process until the trailer is clear of the front of the boat. Some people paint their boats on the trailer, wait until the paint dries, reposition the boat on the trailer, and then paint the spots that were covered by the rollers. Blocking up a boat is a serious matter so if you decide to do make sure the places were you block up the boat are secure and won’t sink under the weight. Don’t spend any more time under the boat then you have to and don’t forget to paint the outdrive if this boat is an I/O. You should investigate what it would cost to have a marina paint the bottom. I have a 23’ it runs me around 10$ a foot and I let them do it.