I recall Paramount Airways (Bristol based operator) 22 years ago. An F/O with around 3000 RAF hours (including multi engine jet command) and two years 737-200 F/O time with Paramount. He switched to the left seat for two weeks training and awarded a command. There was none of this myriad of theory and simulator bashing to make the Right Stuff.
When asked why the F/O got a command so quickly, the chief pilot, Captain Mike Kennett, replied that the F/O had flown with the company for two years and had not only flown all the routes but knew his job and proved to be a good pilot. All that was needed now was to switch to the left seat for taxiing practice using the nose wheel steering and from then on he was on his own as a captain.
I thought that was a most enlightened approach to the question of command training and the F/O proved to be a first class captain. I know this because I flew with him on many occasions and he was light years ahead of some of the puffed up other four bar morons I have crewed with in my time.