Can't answer the splitting parts.
But for the using portion yes, decant most of the liquid leaving enough to allow you to swirl up the cake, then pitch slurry (Cake+small amount of started beer)
For the smack pack, Smack it and wait until it swells tight. then pitch into starter I would assume. This will prove yeast viability before pitching it into the starter.
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I should have stuck to four fingers in Vegas. :o - marubozo's mom