Definately deglaze the pads and discs. It might be that the return hoses are blocked and are causing the pads to stick on a bit. This will cause them to overheat and polish the surface. I would definitely check the hoses. If this is the problem get it fixed soon as the heat can cause the grease in the hub to melt and run out of the bearing. Obviously this will wear out the bearing.
you have to find a dead flat surface and some coarse sand paper, remove the pads, and rub them up and down the sand paper until the surface is fresh and rough all over (no longer polished). It is also worth giving the discs a good rub down with the sandpaper to get rid of any shiny spots. Always remember that the pads might need to be bedded in a bit but it should cure any noises for a while. (Maybe not long enough to make it worth all the effort though).