To achieve a smooth flow when transferring hot wort, ensure that the tubing size matches the fitting. For instance, don't use 1/2" tubing if the hose barb from the valve is only 3/8". To prevent air bubbles and achieve a good flow, pinch the tubing a few inches from the valve, pull it down below the valve, and slowly open the valve. Once the liquid level goes below the valve in the kettle, a siphon effect will help transfer the maximum amount of liquid.