Yeast will keep in the fridge in solution for quite some time. Can't remember the type i used but there's a brewers yeast that is sold in liquid form that's very good. As for propagating, take a packet, activate, give it some sugar, let it kick off, seperate into canning jars, seal and refrigerate. I have some of the "seasoning" prepped now. I'll see what it does and report back on success or failure. It smells good though.