IF your hands are big enough, the "pinkie under" hold is proper, or at least a viable option. This is where your strong hand's pinkie (smallest) finger goes UNDER the bottom of the grip. Under recoil you let the gun "uncurl" the pinkie, and then to bring the barrel back down after a shot the pinkie is used to help by "re-curling". This hold also helps you "index" the gun, in other words makes sure it goes into the same place in your hand before every shot.
The pinkie-under hold works the same whether your off-hand is helping or not. Remember that the SAA-family guns like the NewVaq were originally meant to be fired from horseback, one-handed. I recommend learning to shoot them one-handed, and then for two-handed use transition to the "Weaver" type hold instead of Iscoceles. In a Weaver-type two-handed hold, the strong hand's usage is the same as it would be one-handed, with the extra hand added for control. In Isosceles, the "feel" of the grip in the strong hand changes as you transition between one-hand and two-handed shooting - the angle of the barrel as it leaves your hand is different.
Some decent pics of Weaver and variant holds are at:
http://www.shootingtimes.com/handgun_reviews/st_stayingstance_200803/index.html
Make sure to check the pics in page 3 of that article to see the Isosceles hold. One point I disagree with Sheriff Wilson on is that in either the classic Weaver hold or the Isosceles, the knees and hips can be bent to allow more movement options than he shows. In the hold he recommends (basically an "aggressive combat Weaver variant" sometimes known as the Chapman), he has the foot/leg placement correct and then he stretches and "solidifies" the upper body hold while still doing the asymmetric arm placement that characterizes the Weaver as opposed to the symmetry of the Isosceles.
For a close-up view of the hand positioning, see also:
http://www.globalsecurity.org/military/library/policy/army/fm/3-23-35/chap2.htm
DO NOT do the "cup and saucer" hold they show in picture #3. Do one of the two hand positions in pictures 2 and 4, whichever works for you. In an SA revolver, pic #4 on this page is what you do if you're going to cock it with the weak-hand thumb, while #2 is for strong-hand cocking. I'm a proponent of strong-hand cocking because that way, I'm doing the same basic thing while shooting one-handed or two.
In the holds pictured in #2 and #4 (and again, both are correct depending on your needs), you are PUSHING with your strong hand, pulling with the weak. This stabilizes the grip.
Here's another series of pics of the holds in question:
http://www.corneredcat.com/Basics/stance.aspx
Where I disagree with her is in how she handles the Weaver and Chapman holds. As seen from above, I like to keep my strong-hand forearm lined up DIRECTLY with the barrel, when shooting one-handed or two. That means that my hold is more asymmetrical than hers is - my upper body is turned more deeply to my right (as I shoot right-handed - all of this can be reversed for left-handed people of course).
She's also not emphasizing "bent knees" enough. Lower makes you a smaller target, and bent knees means MUCH faster movement in any direction. OK?
What else...let's throw one other oddity in there. I'm right-handed, LEFT EYED. To find your eye dominance:
http://drawsketch.about.com/cs/howtoindex/ht/eye_dominance.htm
http://www.golf.com/golf/instruction/article/0,28136,1565286,00.html
What this means is, while doing a "regular Weaver" (both elbows bent for close-range, fast shooting) I flip the gun slightly on it's side, bent to the left about 15 degrees, to line my sights up with my left eye. But for distance shooting, I can straighten my strong arm, hold the gun with the sights perfectly vertical and then rest my right cheek on my right arm's bicep, which flops my head over to put the sights in front of my left eye. This forms a "cheek weld" similar to what riflemen do, and is VERY solid for long-range shooting. In this variant my body position is very asymmetrical and my left elbow is pretty radically bent. This "cheek weld Weaver" weirdness is only available to those who are "cross-dominant" - hand and eye dominance are opposite.
Back to holding the gun:
If your reach to thumb-cock the gun with your strong-hand thumb seems to be too long, consider swapping hammers, either to the lower-slung Ruger SuperBlackhawk hammer (same as what Ruger ships on the "Montado" model New Vaquero variant) or to the even-lower Bisley hammer. The SuperBlackhawk hammer can be mail-ordered and dropped right in; I bolted one very easily into my New Vaquero 357:
The Bisley hammer fits, but you have to grind a little bit of metal off it on the back edge of the hammer away from where it fits the rest of the lockwork, so it's not anything needing precision fitting.
If your hands are too small to allow pinkie-under holds to be comfortable, that's OK, it's just an option for those of us with bigger hands.
Sorry if this is more info than you asked for, but, in my opinion every part of your handling of the gun has to be right from literally fingertips to toes.
