In "Theory" You should be able to take a student, and just fine tune their skills to demonstration level, introduce leadership teaching skills. And in Theory it should be possible to go through the course in 10 days.Doing a DM isn’t like doing any other course in scuba. It’s like a mini-apprenticeship to the dive shop. Most skills learned aren’t specifically related to safety nor in-water dive skills.
In practice it's another thing. Most candidates require lots o remedial work to get them to the entry level
I feel that it takes 3 months for a candidate to develop the leadership skills - especially the 6th sense. When people bang on about CMAS 3* - I remind them its club diving so you know each divers abilities. Not so when its customers off the street
My DM's were taught the carry out the skills circuit while neutral (when practicable) This is in a pool with max 6' not on some platform at 15'
Get a good instructor and a DM course can be incredibly valuable especially with the practical skills that are refine. But like any course the end result is only as good as the instructor and afterwards the candidates' desire to maintain their skills
In my time I've had quite a few "tech" divers on the boat whose fundamental skills were appalling.
With regard to Rescue. I prefer the candidates to have reached a level where they can sort themselves out in the water without becoming flustered. We would try only to run it with a group of candidates so that we run all sorts of scenarios to get them the best learning opportunities
But for those wanting to get their DM in 2 weeks - forget it you'll learn nothing. I hold them in the same disdain as instructors who pay for their 1st 25 certs to get MSDT