I've been washing yeast using this method for a couple years now: https://www.homebrewtalk.com/f163/yeast-washing-illustrated-41768/
I generally use the washed yeast from 1 jar in a 1.7L (ish) 1.035 (ish) starter on stirplate for 24 (ish) hours, cold crashed & decanted, in my beers (5gal, or...