My experience is
A) gelcoat is white, not blue
B) some bare spots are no big deal, even if it's bare to the gel coat
C) brushing the gunk off your hull every couple of months with a soft bristled brush dramatically improves the working life of bottom coats, even ablative ones
D) it pays to have an extra coat of ablative thrown on while you're out of the water
E) people get freaky about their bottom jobs, but in florida where boats never come out, you can make a bottom job last two or three years if you don't mind going over with a snorkel mask and a brush while at anchor
Oh, and F) pay someone to do your hull. Don't do it yourself. I've done it, I'm glad I did it, and I sneezed gelcoat dust for two months afterwards, so I'll never do it again.
beej67, Checkered Past, 1980 32' Pearson 323, Panama City FL