As far as the basics of thumbs forward, here's some pointers Coboblack:
Primary Hand:
-Web of hand as high on the grip/grip tang as possible
-Gun as centered in the wrist as possible (Grip the gun, aim downrange one-handed, is the gun centered on your wrist and straight down your arm, or is it cocked to the side a bit?)
-Thumb flagged high NOT clamped down on the grip (This will make sense later)
-Fingers wrapped around grip
-Hand squeezes front to back (Don't think about squeezing with your finger tips, think about pulling on the front strap of the grip and pulling it straight back into your palm. Subtle but can make a difference)
-This hand should NOT be white knuckle gripping the gun. Think ~50% grip pressure.
Support Hand:
-Wrist rotated forward, locked out or as close to it as possible
-Thumb will be pointed downrange
-Fingers will be at a 45 degree downward angle
-Wrap all 4 fingers around the primary hand, TIGHT up under the trigger guard (don't put the index finger on the triggerguard, does absolutely nothing for recoil control)
-Rotate the base of your thumb up as high as you can get it on the grip. Focus on clamping the base of your thumb into the highest part of the grip/frame that you can. (The more you rotate your hand, the more your wrist locks out, the straighter your support arm becomes, the higher you get on the gun = maximum recoil control + consistency)
-Your thumb will now be pointing forward. Gun hand thumb can come to rest on the back of your support thumb, and for guns where you have interference with the slide release or decocker, you can use your gun hand thumb to "grab" the base of your thumb bone/palm area.
Cliff Notes:
-Empty hands, no gun, try this for demo to start getting the feel of this grip
-Make a "V" with both of your hands.
-Point both thumbs at the target (Thumbs will be straight, both wrists locked or nearly locked out, fingers at 45 deg to the ground)
-Close 3 bottom fingers on the gun hand, index finger straight (Hey, getting some trigger index practice!)
-Wrap 4 support fingers around the 3 gun hand fingers (think of gripping a gun grip)
-Clamp support hand down on gun hand. Think about clamping base of thumb into the extended gun hand index finger
If you did this right, you end up in a close to good upper body stance that should resemble some form of Isosceles. You end up close to how you'd want to grip the gun in thumbs forward. This pretty much gets your whole upper body stance 80-90% of the way to where you'd want to get it, and the rest will depend on your own unique physiology.
Golden nugget:
The support hand wrist is crucial to achieving the performance improvements with thumbs forward. Little differences here make a huge difference with everything else. What helps you get close to ideal is how you think about it. Think about rotating the wrist forward as far as you can without causing significant discomfort. More importantly, think about clamping the base of your support thumb into the highest point of the grip that you can. The more you rotate that wrist forward towards being locked out, the higher it brings the base of that thumb. Most people want to squeeze side to side with their whole support hand, and they usually do it 1-3" lower on the grip. Instead of thinking about squeezing side to side, mentally tell yourself that support hand is a C clamp, and you are clamping the base of the support thumb into the top, side of the grip. That subtle difference in how you squeeze, as well as that 1/2" to 1" difference in height of the support hand on the grip is what makes all the difference in the world with recoil control on semi autos.
Here's some pics:
tn_8 by Dillo Dynamics, on Flickr
tn_9 by Dillo Dynamics, on Flickr
tn_41 by Dillo Dynamics, on Flickr
tn_18 by Dillo Dynamics, on Flickr
Important Note!
Here's how a significant number of people shoot thumbs forward, or start out shooting it. This gets you ~75-85% of the performance. Notice the difference? The first pics are support wrist locked out and as aggressive as possible (for me at least, everyone is different). This picture is with the support wrist backed off about 15-25 degrees (I'm guesstimating). THAT is the distinction I'm trying to make here. That few degrees of difference makes a huge difference in recoil control. Thanks Rob for being the guinea pig for these pics. We'll get that grip tweaked yet!
tn_30 by Dillo Dynamics, on Flickr
And here's what I mean by grabbing the back of the thumb bone/base of palm if you have issues with your gun hand thumb interfering with the slide release or decocker:
Again, great info brother, appreciate it.