How much liquid culture do I use per jar or bag of grain?

A common rate is 2 to 5 ml of liquid culture per 500 grams to 1 kg of sterilised grain. More culture speeds colonisation and lowers contamination risk because the mycelium takes hold faster, so err on the generous side when your culture is clean. Shake the jar once you see healthy growth to spread the mycelium and cut colonisation time.