I take the thermostat out and use distilled water with the heat going a couple times then put a new thermostat and gasket in with some 50/50 g-05(4Gal).

I don't use a flush chemical.

Is there a better method? I've seen older mechanics use a garden hose for the pressure to get it more clean with the vehicle off. I guess this doesn't do heater core.

 

Are you draining it out and refilling? You don't specify. A backflush would be better IMO. You can buy kits to do this.