M_Boats: Filling, Fairing and Painting

My M15 has a few gouges and scratches on the forward end sides and bottom of the keel. I will be filling/fairing these with a) West System with micro fiber filler *or* b) Evercoat Formula 27 Filler. Which would you use? Second, these filled areas must be finish painted (I believe). What paint (or ought it be Gelcoat) would you use beneath the waterline on this job? I have no bottom paint on my boat. Thanks again....... *Jeff+* Molōn labe!