Coating the piston will not increase compression as it is already going to be as close as I dare to the head, with a film on it i will have to reduce piston to head distance the same amount. It would still have the thermal benifit but I would have to measure and make nachos in them before the coating, also if I get too close it will touch the head and possibly mess up the coating on the head and the piston...

Is there any good DIY kits that you know of?