You should have the regulator at the bottle, then hose to a 1/4 turn ball valve for quick on/off then the needle valve to adjust volume of gas and fine tune the gas on a blown forge. The needle valve does not control pressure, that is done at the regulator, the needle valve only controls volume. You should have a gate valve between the blower and the gas inlet to control volume of air. With the gate valve and needle valve you can control the relation of air to gas, very much like an ace/oxy torch.
Let me know if I can help you.
Wayne