Actually the thumb trick is old skool and works well. Reason why I dislike it is that your thumb gets all fucking sticky. As for your finger being too close to the nail, you still need to get pretty close to burn yourself from radiant heat, especially if youre drawing cool air in at the same time by hitting the rig.
In either case, at a distance like that you would feel enough pain to move your hand but not enough to cause serious injury IMO. Hell, before I got my thermal gun, I would hold my hand over the nail @ ~.25" to see if it was ready to dab. If its not hot enough for you to move your hand, its good to go... usually.
edit: LOL we have the same torch. BBB?