Many aircraft didn't really have a lockable tail wheel and this is reflected in CoD.
Rudder effectiveness is a matter of airflow, if you go too slow it won't do much. Also, the torque and propeller effects are more pronounced at high power settings and low speed.
So, if you step on the brakes, apply full power and then release them for take-off, all you are do is create a situation where you have the most amount of torque with the least amount of rudder control to correct it in an aircraft without a lockable tailwheel
Like others said, build up your power gradually. You don't need to do it slowly, just gradually, don't start your take-off roll by slamming the throttle to the stops.
This allows the aircraft to get rolling at a speed and power combination where the torque effects are less pronounced, while at the same time putting some air over the rudder to enable it to work, then you can give it more power and take off.