Yeast Starter

I am making a yeast starter from a pack of Wyeast 2035. Beersmith tells me that I need 500billion cells. So I went ahead and made up a 2 liter starter. If i am correct this should give me 200Billion cells? Then I decanted off and added another 2 liters of wort. According to various charts that should give me 300 Billion cells? That is where i am stuck? Can i just carry on doing this 2 more times to get 500 billion? Or does the restrictive size of 2 liters(i only have a 2l flask) make this impossible? Any help would be appreciated.

The problem with stepping up so high and only one flask is that there is a diminishing yield/growth of yeast with each successive addition of fresh wort, due to the already high cell count.  Your best bet is to make the first step at 2-liters and then divide the resultant slurry in half and repeat with each half at 2 liters.  This should get you up to around 400 bil cells.  Then split and repeat one of the flasks for your last 100 bil cells required.

OR, what I usually do is make a small batch of a low to standard %ABV beer, since the above will require 8 liters of starter wort (a little over 2 gallons) and use the yeast cake from the small batch for the larger batch.

Thanks, I thought as much. I like your idea of  making a small batch (10L or so) then reusing the yeast cake. You can never have enough beer after all!