the water is what leves marks.. if you rinse with purified water you won have that issue.. many filters are available to bolt on to your hose.

    However.. i find that if the car has a good coat of polish on it that the chamois should lift all the water.

    Clean the car, clay stick it, then polish with a good polish like meguairs gold class, autoglym super resin et al.. use microfibre cloths to buff… if you ahev some spare coin… swiss wax would be a great way to seal it in.