IMHO, if you want to sail now, just apply antifouling paint and then splash the boat. If you want to apply a barrier coat next year, you will have to strip off all the paint (new and old) before you do.
I went through the paint strip, fair, barrier coat, bottom paint process this past winter. I did a write up on it, which you can read about here:
bottom paint 1, me 2, all done, test