i have a 21' .I sand what i can reach with a palm sander on the trailer, then CAREFULLY winch the boat back about 1 foot and sand the rest. Then i paint it in this position, then pull it back on (day later) and finish it up.
Good Luck
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Things done at the last possible minute are done with the greatest possible information. Procrastination is, therefore, the most efficient means of doing things.