With handwarmers, you’ll see evidence you’re ‘on’ in the thermal….heater will get ‘smeared’ or leak heat in your viewfinder. I generally send two more, then walk to it or use a spotter to check the group. I’ll also set up 3-4 ‘heated’ targets, with the handwarmers folded in half. Toe warmers with the sticky back are a better size, imo. I’ll also tape some to the backside of my steel plates for ‘play’.
