I am unsure about the whole first finger method. I have always taken a more whole hand, all fingers in balance approach. In fact, Shinichi Suzuki always instructed that to press with the first finger concentrates weight at the lower part of the bow but does little to help with tone at the upper and tip of the bow. He always said never even use the “P” word! He stressed rather, the balance between the strong thumb pushing upwards, fingers on top responding with slight firmness in tandem and generally leaning back on the stick so pinky stays rounded and elbow stays low and relaxed. One exercise often used was to hold the first finger off the bow and play with all the other fingers, to discourage pressure from the first finger and its resultant bad effects. I tell my students to ‘squeeze’ the bow for heaviness at any point in the bow stroke. It doesn’t take much. But all the fingers work together. Pressing and focusing on first finger influences the bow grip to lean in (toward the tip), while ideally fingers should lean back on the stick (toward the frog). When the grip leans in, all sorts of bad things happen and I have seen this many times in my studio and here on the site. Pinkies straighten out and don’t develop back of the hand strength. Elbows raise up above the bow stick which is inefficient. Wrist bends up which is a terrible stress point. Knuckles rise up and carry the bow, instead of laying nice and flat, sort of like a tiger claw. It’s very difficult to hold and use the bow correctly, but if you look at the great players you will see this consistent position of the fingers and overall strength in the back of the hand.