It is difficult to gauge just how much help that one finger from the non-working side is actually providing us, though--that's where the assistance of a rope that doesn't stretch and a light weight on the floor comes in. I would also recommend investing in a small pulley for the bar and rope, so that there is zero friction (which would make the drill easier--we can't have that). Dudes who previously thought they were close by using that one finger suddenly find to their dismay that they weren't nearly as close to the one-armer as they thought after they try the pulley rope.
As the tutorial mentioned, if the non-working side is helping us too much, the weight comes off the floor, and we won't go anywhere. As a guideline, I believe that if you can't do this just yet with a 12 kilo kettlebell or less, don't even worry about this method until you can. Go back to weighted chins and work up to chinning yourself plus half bodyweight for at least a few doubles or triples, then give it another go.
Many ways to skin this cat for putting the plan into effect. I personally liked the GTG approach, and it was always a happy day to find I needed less and less weight tied to the other end of the rope as the weeks and months passed. However, these are very taxing, and we need looooong rest periods between reps. On that note, you might find your arms/elbows simply ache too much to GTG this one day in and day out. I'd recommend at least one day's rest in between, or maybe even two. At the risk of sounding redundant (did I already say that...?), we don't want to rush this process. Listen to your body, especially your elbows, and proceed with caution.