Starter for 10gallon batch

I want to make a starter for my first 10 gallon batch of brew. I have done starters for 5 gallon batches in the past and just pitched the whole flask.

Since I only have one flask & stir plate how do I split my starter for two fermentors? Do I just pitch the whole thing into by brew kettle after the wort has been cooled, stir it and transfer into my 2 better bottles?

I don't have a single fermentor that will hold the 10 gallon volume so I will be using two better bottles.

If it were me, I'd probably make sure the starter is nice and shaken and do my best to split the starter amongst the two fermenters. You can decant, if you prefer, but just make sure it's well shaken so you get a reasonably even distribution of yeast. I prefer to add my yeast into the fermenter, rather than my kettle, if only because the larger hole in the kettle makes more room for nasties to get in than the relatively small hole of a fermenter.

For a 10 gallon batch split amongst fermenters, you'll want twice the amount of yeast, so that means doing a 2L+ starter or, better yet, a stepped starter.

For a 10G batch I only go up to 1.045 or 50. Use Mr malty. About 2500ml on a stir plate with a fresh vial works for me. I decant the starter into .5G jars after 24 to 58 hours and chill. Then decant off the yeast and swirl the last bit and pitch into 5G of wort.

BW

I make starters all the time because I usually brew 24 gals. I keep it fairly simple and it works out well from my experience. A general rule is to use a 10% starter based on the brewing size. So a 1/2 gallon starter made several days before you brew would work well. I make a 2 1/2 gallon starter using DME to grow more yeast. 1/2 lb DME in a 1/2 gallon starter would give you about a 1.04 O.G.. Most my starters are less in the O.G. unless I'm making a big beer. 3/8 lb of DME in a 1/2 gallon starter would give an O.G. of around 1.03. I find this works well for me when growing more yeast ahead of time for batches larger than 5 gal.