I have a Heli-Coil tool that has a stepped tap that taps the hole out to the proper size for the Heli-Coil insert. I open the intake valves, remove the carbs and blow shop air into the intake. The chips come flying out the flute of the tap. When I am done I have a piece of steel brake line that goes on my blow gun which I use to blow in the cylinder removing any of the chips that did not blow out during the tapping process. I then spin the engine over with the plugs out to make sure anything left gets blown out of the exhaust port. The hardest part of the whole process is getting the "tang/tab" off of the insert. I have modified a pair of needle nose pliers to hold the tang/tab and then I strike the other side to break it off.
Over the years I have probably done close to 100 repairs this way. I don't know of any other way to repairt the threads in the car.
Also, you should never use anti-seize on the sparkplugs. The oils in the anti-sieze compound burns away leaving the metallic part of the compound to gall the threads when the plugs are removed. The biggest problem I have found that creates this issue is that the spark plugs do not stay tight. They must be tightened after every race night. The aluminum and steel expand at different rates and the sparkplugs come loose. I have found by tightening the plugs during the nut & bolt session before an event, the plugs will be loose most of the time. Keep them tight and they should not gall the threads, thus damaging them when the plug is removed.
Randy - RPM