And for what it's worth, our DM classes take on average 6 months to complete, some a little less and some that strech out to a year. It takes that long to work in all the requirements our shop has, amoung others, we require you work with 2 full OW classes, from the class orientation day to the wrap up day and every day inbetween. If the course is a 4 or 6 week thing, your not getting your moneys worth.
I agree here on this point. But 2 full OW classes should be the MINIMUM. Like many other things, you should review to say whether you really are ready after that. If not, be honest with yourself and the instructor and tell him/her that you'd like to assist more classes.
Don't go for those "Boot Camp" style DM classes. Yes, the basic skills and information portion will be the same. But no simulations can prepare you for the actual events of assisting with actual classes. Managing and preparing the site, assisting students in setting up, maintaining organization in and out of the water, etc.
You'll never be able to simulate some of the real-world events that students tend to be involved in. I've had DM candidates actually be stunned by what they see now in their new capacity.
When training my DMs I would give them DM responsibilities with another instructor's class while I "flew wingman" over their shoulder. I would only intercede when student safety or class flow was being comprimised. Then we would debrief the event, covering what went right, what went wrong, how they could improve, what they saw in instructor technique and how they felt about it. This last one prepared them for developing their own style as a professional. Your DM instructor has to be a mentor, a much more involved position than that of instructor.
So bottom line, if you want it fast, and you want it bad, that's how you'll get it - fast and bad. Like many of life's best events, it's the trip that makes it, not just the final day. Enjoy and learn all you can. If your instructor does all that
herman suggests for a private course, they'll earn every penny of that fee.
If you're just going for the card, save your money and put it toward a great trip.