I store my stocks in 2ml cryovials at -80c. When I want to grow stocks, I scrape a pipette tip worth of the solid into 3mls of 10% dry malt extract (100g/L) and shake at 30c/200rpm for 24-36h, basically until turbid. Then I inoculate 50mls of 10% DME at 18c/200rpm for 24h and then inoculate 1 to 4 L of 10%DME (depending on the target beer's OG) for another 24h at 18c for ales or 48h at 10c for large strains, again at 200 rpm on an incubated orbital shaker. If I'm in a hurry I centrifuge 6000xg for 10min, otherwise just crash cool and decant the bulk of the supernatant, leaving the yeast matter behind.