I've had my boat on and off the trailer several times in the garden & it's a doddle if you've got space, old carpet & some decent wooden chock lumps. Here's how I do it:-
1, Put the trailer with the boat on it, exactly where you want the boat to end up when it's off the trailer, e.g. middle of lawn, move the croquet hoops first.
2, Fasten the towing eyes on the transom to an immovable object, e.g. other car, in my case eyebolts set into the floor.
3, Remove all straps holding boat to trailer (important this bit) & slowly drive the tow car forward. The boat should stay where it is & the trailer will roll out from under it.
4, Pull forward about a metre & start to chock the hull either side of the keel, using blocks & old carpet to protect the hull, repeat until boat is off trailer & sat on blocks.
5, to get the boat back onto the trailer, reverse trailer up to boat, attach winch & pull trailer under boat, removing the chocks as she goes on & voila!. Done this a few times when I've needed to work on the trailer & it really is a doddle, as long as you have plenty of room, chocks & carpet.
Rule#2: Never argue with an idiot. He'll drag you down to his level & then beat you with experience.
Rule#3: Tha' can't educate pork.
Rule#4: See rule#5