Saving a commercial beer yeast

I saved out 250ml of my second runnings 1.031 I want to try to harvest the yeast from a commercial dark wheat I have been enjoying. I’m going to use it in a dark wheat I’m going to make. Now the beer comes only in 22 oz bottles. How many do I need the yeast from and what is the preferred process ?

first off, if your going to harvest yeast from commercial beer don’t expect it to be good for your beer. don’t let that statement stop you from trying it. the thing with yeast in the bottom of beer bottles is they may have been finishing yeast or they maybe the last ones to drop out of suspensions and that is going to change the way the yeast act in the next generation. now this does not mean they are no good, you just have to try it and see.
when you do it, take and save the yeast from the bottles and make a starter, run that starter though till its finished- 24 hr or so. Use wort from prior batches for your starters. 1.04 is good, then see what you have. you need 2ozs (shots) of settled yeast to ferment 5 gal . with out getting all science and measurements here I would shoot for at least 1 inch of settled yeast in the bottom of a quart jar.
how many bottles do you need, well that all depends on how much yeast is in the bottom of them bottles. from what I have seen in some bottles I would use at least 10 for a starter but I’m really no expert at this. now this has been my opinion , and as we know we all have them, but this is what I would do. P.S. let us know if this all turns out.

Poured one bottle in 250ml yesterday. Today there is sediment and krausen. In another day I plan on decant the old wort and add about 500ml of fresh wort pluses the dregs fom another bottle. I wish I saved out more wort. Ill have to use some DME .