Are you talking about working the yeast back up into a pitchable volume? To me, "growing a yeast bank" just means collecting more strains.
I did this for a while but then found i wasn't brewing with enough warning to get to a pitchable volume. But basically you just grow a serious of starters preferably on a stir plate. from a slant I would start with 50ml and then double the wort volume about every 48 hours. So in my case I'd go 50ml -> 100ml -> 250ml -> 1000ml then either pitch or go to 2L depending on the batch gravity.