I got mine for removing Harley case screws many, many years ago. It will help loosen the screws if you hit them several times fairly hard with a punch and hammer. If the slots are worn, you can use a flat punch to force them together a little and then drive the bit back into the slots. This will tighten the fit and will often ease the tension and corrosion enough to free stuck screws.
Use an extension that is as short and fat as possible to maintain the impact shock effect. A long slender extension will greatly reduce the effectiveness of the driver.
Don Young