throughts on starter step ups from frozen yeast

I have access to a -80C fridge and was planning on starting a yeast bank. What I would do is upon opening a white labs tube or wyeast smack pack freeze down 20 vials of 1ml of yeast with an additional 300 ul glycerine. I would like to use the least amount of step ups to get to a final of 2L along with the least amount of use on a borrowed pressure cooker. What would be the easiest way to do this?

It's a long article, but I'd suggest you read this:

http://www.maltosefalcons.com/tech/yeast-propagation-and-maintenance-principles-and-practices

The article speaks about building up pitches from very small colonies of yeast. Hopefully it helps.

My procedure is something like this, not the 'least amount of steps' but rather a slow, sure and safe way:
Frozen yeast, slant, 5ml, 20ml, 100ml, 500ml, 2L

The slant allows me to visually check the yeast viability after coming out of the freezer, then the small steps help 'proof' the yeast, keep any infection sources under control and hopefully get maximum growth and health from the yeast at each step.

In theory with sterile conditions/media you could go directly from the freezer to the 2L starter, or any number of intermediate steps, if the only criteria was 'least number of steps'. However, depending on what/where you read, steps of about 6-10x are usually recommended.