Growing large amounts of yeast

[Vertra]

I was wondering what the best approach would be to growing a significant amount of yeast from a single vial would be. I am using a 5000ml and a 2000ml flask, plus I have all sorts of growlers laying around. I also only have one vial of WLP099 that I need to grow into 4 viable starters to pitch into already fermenting wort. I have already made a single 2000ml starter in my 5L flask and plan to step it up but I am wondering what the best time to transfer into new vessels would be. Should I cold crash, decant, and pitch new wort into this vial again... or should I start splitting it up earlier? How frequently should I be stepping up? It has been going for 24 hours now.

Im not really sure how much I need to make since Mr Malty cant calculate how much I need for a stuck fermentation. I need enough to pitch into 4 fermenters of roughly 1.040-1.045 gravity wort down from 1.090+ OGs from a single vial of WLP099.

Thanks in advance.

 

[badbrew]

Step it to 4L, swirl, divide, chill, decant, pitch.
How much did you use in the beginning and how long has it been?

 

[Vertra]

The original 2000ml was using the 10ml per gram of plain light DME ratio and yeast nutrient. The fermenters I am pitching into got a 1 quart starter with pure oxygen aeration and yeast nutrient and went from 1.108 to 1.040 on their own. Considering how seriously under pitched they were id say they did decently well.

So I should chill the 2000 I have now and decant it, then step up one more time to 4000ml. Chill, decant, then split evenly into 4 containers. Then step each of those up? How long should I be giving these starters before chilling? 24 hours? 48 hours?