If you carry a revolver for self-defense, you need to be training to shoot accurately and quickly in the double-action mode.
Trying to manually cock the hammer on a revolver means you have to change your master firing grip between each shot. This is not good for accuracy nor is it good for weapon retention. Defensive shooting should be done in the double-action mode.
Shoot as Fast as You Can Hit Accurately
Your training should be outcome-based. Adjust your speed to get the outcome you desire, then pick up your speed as your skills improve.