hi there ive got a blockpaved patio which was sealed with resiblock superior some time back but has marks under the sealer which annoys the hell out of me ,im looking to remove the resiblock and recoat ,what would you recomend ive tryed powerwashing and even dry sand blasting but no joy .Ive just come accross a karcher wet sand blast attachment on ebay has anyone tryed on many thanks in advance.