I don't know if this plays into Brad's technique or not, but for me, the biggest challenge to achieving a consistent grip was actually my elbows. I tried bracing my arms every which way and battled the thin line between too much and not enough support. If I kept my elbows off the table, muscle fatigue would show quickly in my groups. If I sprawled myself on the table and supported my arms too much, they didn't move through recoil consistently, and things changed every time I made the least bit of adjustment to the pads, towels, etc.
Some of the best groups I shot from a bench with a revolver were literally after I said "to heck with it all", threw a towel over my range bag, and used that to rest my forearms on but not my elbows. Sitting bolt-upright in a chair with both arms extended in an isosceles pattern, elbows locked firmly but not hard, forearms just propped on the towel-draped shooting bag, and barrel just barely resting on a flat block (also with towel on it), seemed to work pretty well and I could repeat it. The trick was being able to put the same amount of "preload" on the revolver, as told by how much of its weight I was letting sit on the barrel rest and bag. After cocking the hammer I would slowly lower my arms and the revolver together to touch the rests, just barely, using the rests to steady my arms and the barrel but never leaning on them or slouching on them and always trying to maintain the same pressure by feel. That way my body was moving with the recoil the same way each time, and the follow-through was a lot less choppy. It seems weird that I could hold the revolver better than I could rest it, but I think the answer is in follow through and having a way to feel how much the whole support system was preloaded. The rests were just there as pressure point gauges and to soak up muscle tremor and wiggle, and if I allowed the weight of my arms to be supported too much, sooner or later I'd start to relax my shoulders too much, or my triceps too much, and groups would start to go wild.
I had this wacky idea that a vee-rest for the barrel would be the best. I tried and tried but never made it work, always there was horizontal stringing. With a vee, I was subconsciously leaning just a titch or pulling to one side or the other, and the vee masked that. Using a flat surface under the barrel, and supporting 75% of the barrel weight with my arms, almost floating the barrel off the single-thickness terry towel on a stack of concrete blocks, made me focus on not putting any side load on the revolver.
This is probably all wrong to suggest, and I'm not suggesting it necessarily, but it worked for me. I don't know if this will work well at 200 yards, but it allowed me to shoot a lot of 3" groups at 100 and a number of them smaller, without thousands and thousands of rounds of practice and no one to teach me. This has to be a little like High Power competition, minus the bob and weave. YOU are the supporting mechanism for the gun, the jacket is just there to give your body a reference position, a little bit of support, and to soak up twitches and tremors. Lean on the rests too hard, and you lose control of the gun....unless you're shooting a benchrest rifle which you want to do the opposite and touch the gun as LITTLE as humanly possible and make the bags do 100% of the work.