backslopping whey?

[Bernardsmith]

If I want to experiment backslopping whey to culture my milk should I allow the milk to sit for longer than if I simply add kefir made from grains? And the whey I use to backslop - should that be quite fresh of should I allow that whey to sit for a few days? Should that whey be aged in the fridge or should it be allowed to age at room temperature? Thoughts? Thanks.