Regarding gripping a single action revolver, I've spent a lot of time with a Ruger Blackhawk in 45 Colt for some years now, and here's what I have found. You mileage may vary, though.
I shoot it best when I rest my shooting hand pinkie sitting under the grip. So, the index finger is the trigger finger, middle and ring finger around the grip, and pinkie goes underneath the grip. This helps to keep the gun from shifting down in the hand in recoil with that rounded, plow handle type grip. I curl the shooting hand thumb downward, same as for shooting a double action revolver.
I use my off-hand thumb to cock the hammer, and I found that putting my off hand index finger around the front of the trigger guard (like the shooting style that was in vogue in the '80's) helps put that off hand thumb in a good position to cock that hammer.
Hope you enjoy that Blackhawk. I sure love mine.