I'm looking to paint over my pebbledashed external walls to hide some rust staining that is bleeding through - the source of rust is galvanised screw heads holding an metal lattice on the wall to the which the pebbledash was applied. Has anyone come across this problem before? If I simply paint over with masonary paint will the rust bleed through? I'm keen to avoid a job I know will be hard enough if it means I'm forever touching up rust spots - any advice would be much appreciated.