Be careful cleaning the tops of the pistons off. It is easy to end up with a bunch of carbon grit stick down along the sides of the cylinder walls and chew up the cylinder and rings. I would just carefully wipe them off with a paper towel and leave it. If you use a wire wheel to clean the chamber/ports at least use a brass wheel that won't remove a lot of aluminum along with the carbon buildup. I prefer to use a scotch brite pad. What I do is use a 1/4" mandrel and cut about 1" down splitting the end of it open and slide a piece of scotchbite about 1" by 3" into it. Put it in a die grinder or drill and have at it. Helps a lot to do it in a parts washer to keep washing out the nasty stuff but you could probably do it in your driveway and take turns spraying it with degreaser and water to clean it out. Not a bad time to take it in to a shop to have the valve stem seals replaced and talk them in to cleaning it for you...

BTW I would HIGHLY recommend having your head surfaced while you have it off. If you blew a head gasket, odd are the head isn't straight. Even on the good ones I typically see .005-.008" high/low spots that you might not catch with just a straight edge and a feeler gauge.