My clawfoot was released from a 30 year imprisonment behind a makeshift tub surround. Really bad. so, it is in good shape except for some bubbly looking weirdness around the top lip UNDER the roll edge. ???? The faucet hole seems to be black and pitted but not rusted through. I would like to do a mosaic on the outside of the tub. Any ideas how to prep the surface? steel wool and oil? no oil? would oil interfere with mastic? Should I use mastic for the tile? help please.