I went through this EXACT process with my C&C 37 last season.
With 20/20 hindsight, had I known I''d be selling the boat within a couple of years I would have held off and sanded with what I had. For me, a cruising boat that I raced with would sell more easily with a more normal bottom (as opposed to a racing boat that I would cruise with). I also experienced...complications...which I have detailed in other posts.
It''s all a matter of how serious you want to get with the boat prep. It makes a big difference, but unless you''re dead set on winning all the time where you race you can still have a good time with a smooth, softer bottom.
You have to get every scrap of the soft paint off; in my case we had 17 years worth to get rid of, came off like tar.
Surface prep once the paint is stripped is important too. If you spend the time to fill in the scratches, knicks and dings then the overall results will be better. The new paint will cover SOME imperfections, but it''s a much thinner layer than the ablatives so there is more show through of imperfections. Even scratches from 80 grit paper on a random orbital sander show through three coats, although they can be sanded out.
As mentioned in other posts, VC Offshore & Baltoplate are the most common choices.
I gather these can be rolled on yourself, if you are careful. I had the yard spray it on. There is less sanding involved with spraying, as the initial finish you are working with is smoother and there is less paint.
As far as sanding goes, you will want to do a little, even if you don''t go too far with it. The difference in feel between just-sprayed Baltoplate and BP wet-sanded just once is huge. Basically you work your way up in grits to finer and finer. Do it once at the start of the season. You will want a diver to come periodically; around here they get about $1 per foot.
If you are having it sprayed and are using VC, you may want the first coat in a different color. This way you get a "tell" to see when you''ve sanded through your top coats.