I am planning not to repaint next season. What is the best way to "freshin" up the bottom before launching and when? Also I had a lot of barncles on the prop and drain holes, what's good to paint there?
Just use some more of whatever is currently on the bottom to touch it up. Areas that will generally require touching up are the waterline, the leading edge of the keel and the bottom of the keel, since these are areas that get extra wear.
BTW, what are the through hulls and prop made of?? If the prop is bronze, steel or aluminium, you really should just sand it lightly to get rid of any growth. Then coat it with Lanocote, which should help prevent growth for a bit.
If the through-hulls are plastic... then paint them with the anti-fouling paint.
If they're bronze, then some antifouling paints will cause them problems... so you'd need to check with the manufacturer.
In this area (New Engalnd and LIS), people have very good results using Petit Zinc Coat Barnacle Paint which comes in a spray can, won't hurt your prop or shaft and seems to cut down significantly on the growth over a season. We pulled the boat this winter after 2 years and the prop and shaft were virually free of any growth and we didn't use the boat much this year.