1. Are you working on the strong left hand and weak right?
I wouldn't say the new left hand grip is strong, it is just more heel pad on top with more pressure on the last three fingers and which helps establish more left hand thumb pressure which is something I never ever had before. I don't really fell like my right hand is weak but by pop definition some might say it is. The right hand just fits in better now and if I want I can feel #3 in the waggle and at other times during the motion.
If you are, how does the grip affect the twistaway--do you feel you need less?
For me the twistaway doesn't feel any different with the new left hand grip. If anything the new left hand grip allows the hands to locate a spot at the top much easier. I can control the amount of left wrist cock now much more than before. It is a very secure and powerful feel in the hands.
Securing the hands on the club so they feel more like an extension of the arms and club is another thing I noticed after the grip changes. Maybe this is a big part of clubface control?
2. Can you explain the tumble and how it feels?
I can feel the out part (clubhead/clubface) of the down-out-forward direction of the downswing now.
Obviously the above info is all my "FEEL" based information and everyones's feel system is different but maybe it will help someone.
As far as Brian's descriptions of his information and how he describes components of the swing I have found many of his to be very helpful with my swing improvements. There are tons of gold nugget information in this forum and on the videos, you just have to be patient and look.
Matt