That is pretty cool.
How would you go about propagating yeast off of a bottle of beer?
Now I'm curious!
Its actually quite easy.....you buy a six pack and pour out all but a quarter inch or so at the bottom of a few bottles(make sure you sanitize the top of the bottle)...I used three and just add that to a small amount of cooled starter...and wait a few days...took about 2-3 days before I saw any activity, then you can just step it up with a larger amount of starter..do that until you have enough yeast to pitch
I did it off a bottle of two hearted, but I have heard it is better to do it off of one of their lower alcohol beers, so the yeast is not as stressed, but I didn't have any problems with mine.
there is also a section on doing this in Palmer's book