In a "street" situation, I put my hands up and out, palms facing the other guy, just trying to maintain my space: "Hey, sorry, let talk this out, I am sure we can work this out..." As the guy gets close to my hands, to push me back, I don't have to pull my arm back to hit him. He put himself into the position.
The whole point of the one inch punch training, is to train to deliver a very sudden impact with little to no space. This first strike will give you the opportunity to get to the bigger and better stuff. You can interrupt what is happening, change the dynamic very suddenly with no wind up. But it doesn't have to come (and will probably rarely will) from: "here, let me put my fist an inch away from your chest, while I settle into my stance..." It will more likely be a target of opportunity.
Training it should start in the stance, nice and still, then bang! But thats for learning the principles. Once you learn how to connect your body and explode that way, you need to learn to apply those same principles from other stances and without the stillness.
There is a heavy wooden door at work, that says "Push." As I approach it, I put my hand out to push it open. At the last second, I close my hand into a fist and punch it from half an inch to an inch away. Part of this is to train my hand to hit hard things. The other part is to see if I can punch the door suddenly, from a natural position utilizing the one inch punch principles. Now this isn't a full force punch (yet), I have wussy hands which is why I am trying to toughen them up. But, if you were expecting a gentle push or shove from an open hand, and I punch you this way instead, it will be surprising, I will have got your attention... for better or worse