After scraping with putty knife & wire brush, apply water based POR 15 "Marine Clean" mixed with "hot" tap water. With coarse steel wool, rub greasy areas with 1:3 mix of "MC" to 3 parts "hot" water. (Wear rubber gloves). Solvents & mineral spirits will melt grease, make grease thin, & allow thinned grease to penetrate porous metal. "Marine Clean" will emulsify grease & remove it so one can see bare "cleaned" metal.