I used a single bottle of Bell's Pale Ale that someone sent me in a Secret Santa swap. I just made ~1 cup of 1.024 wort and after I carefully poured the beer (and left the sediment) I flamed the bottle opening and dumped the wort (aerated very well!) right into the bottle and covered with foil. A few days later there was krausen and I just stepped it up from there, in a flask and on a stirplate.
I used lower gravity wort than a normal yeast starter because it can be easier on stressed yeast. I increased the gravity for each step; 1.032 for the second step and 1.040 for the last step.