Well, my alt spent a couple days chugging at 58F and now it's going strong at 62F. I will let it ride there for another week or so before I raise it to ambient for a few days while I let my fermentation chamber take on an IPA. Then I will rack the alt into a corny and pitch the slurry into 12 gallons of Kölsch which I will probably also ferment in the high 50's now that I know the yeast can take it.
I would pitch about 1/8to 1/4 the slurry into the kolsch. (assuming good yeast health, proper oxygenation in the last beer...etc) Pitching the full slurry is just too much yeast. (assuming same batch size).
My personal progression for this yeast is 2L yeast starter -> 3 gal cream ale (1/2 yeast slurry into) 5 gal Alt 1/2 into a 5 gal Kolsch. After that my fridge is full for the first half of summer.
This tends to be over pitching the yeast, but the results are good for me. Based on what I have been reading lately, I think that if I went to pure O2, the yeast health would be better and I could cut down on the quantity of yeast slurry to start.
Either way, keep the kolsch yeast at 52 to 58 and love the results!!!