Hi, new to any forum so have patience. Im replacing a railing in our house with a pony wall with built in shelves. Its going to be about 12" wide and 8' long, my plan is to build 2 frames out of 2x4 and frame shelves in, its going to be painted and i dont know what type of wood will paint best. Unsure of mdf and im on a budget, so recommended thickness and type would be appreciated. Apologize for vagueness.