Have an existing bathroom with partially tiled walls.  Previous owner painted the tile AND grout lines with some type of glossy coating - not sure what it is.  Would like to install pine paneling over the painted tile, and looking for the easiest means to accomplish.  Rather than demo of tile or furring out the walls, was considering glueing of the pine, but the painted surface is rather smooth offerring a limited substrate profile. 

Can gorilla be used directly without surace prep, or do we at least need to expose the old grout lines for a better bonding substrate?  Suggestions?