I take it by renewing the surface you mean to blast off all the antifouling down to the fibreglass substrate. An epoxy coating should then be applied. It is then a good idea to apply the antifouling undercoat when the epoxy is a little bit past ¡°tacky¡± that will guarantee good adhesion. Replacing the thru hull fittings if they have not been replaced in the past 7 years is good advice.