I ordered two of the "Used-Needs Repair" 10'6" Adventurer 2 ISUPs. Both came with tire tracks and footprints and other evidence that the dopes who owned them before me treated them like garbage.
Still, one board required no repair at all, and held more than 12 lbs of pressure for several days. The other one was more of a problem. I inflated it and it lost pressure quickly. I used the soapy water spray method to find the leaks, and all of them were on the seams; either pinhole leaks where the seam was glued, or an area that was longer and seeped air pressure slowly and steadily.
Because they were seam issues, and there were half a dozen of them at least, I wasn't all that confident that using the patches would work due to the uneven surface between the board & the seam, so I purchased a tin of HH-66 vinyl cement from Amazon.
I applied several layers over each of the leaks, and along the seams where needed, letting them cure 24 hours before testing again. In all, it took about 4 days to find all the leaks and seal them up. But the ISUP is now holding pressure and I'm looking forward to getting it out on the water before it gets too cold.
In the end, it was totally worth it, getting 2 ISUP packages for $100 less than the price of one new.