THE place to start is "Shooting to Live" Fairban and Sykes.
Here is picture of one day of good instruction and about 500rds practice can do:
That was done by my dad after 1 day of instruction and practice. The idea being to draw and start getting hits on the centerline ASAP, at about the pelvic girdle and working up to the ocular cavity. The tape was all new at the start of the drill. This is 3 runs with a 16 shooter. Note 1/3 of the shots are in the blue, the remainder are in the masking tape.