DC-3 instructor reported a loss of directional control by a trainee during takeoff roll resulting in a runway excursion. No damage or injuries reported; aircraft was towed to Maintenance for evaluation.

Narrative

Taxi incident at XG02 training First Officer (FO) in Aircraft X on Day 0 at ZZZ.Called FSS on Day 0 at XA49 time requesting and received a standard weather briefing. No flight plan was filled.Ground Taxi Training conducted for First Officer; sitting in the First Officer's seat; in the Douglas DC3TP aircraft between XF40-XG04.FO taxied aircraft slowly down X Taxiway to the approach end of Runway XX without difficulty; remaining on center line. Tower clearance was received to taxi down the runway for training. A 90 degree turn to 360 degrees was made; lining up on the center line; Runway XX. After a short delay power was added to accelerate the aircraft to a speed adequate for some rudder effectiveness. Unfortunately; FO applied abrupt; hard rudder movement causing the aircraft to swerve abruptly. My feet were following on the rudder pedals. Attempted to regain control calling out I've got it two times. Unfortunately; I believe FO and I were attempting to control the aircraft at the same time. Power was pulled (reduced) to idle and into reverse. After several abrupt heading changes we left the runways left side and entered onto the grass covered soil. Due to heavy rain having soaked the ground; the main gear sunk into the ground; burying the main gear up to wheel axles. Shut down checklist completed.Communicated to Tower that we were off the runway and shut down. FBO was called by cell phone.Person A contacted Person B who later showed up with a John Deer Tractor to pull the aircraft out of the mud. That proved not to be possible. Person A contacted Person C at Company towing. Aircraft was winched slowly back onto runway. Aircraft towed to [FBO] ramp and secured.Unfortunately few pilots are trained in Tail Wheel aircraft today. A tail wheel airplane teaches pilot how to better handle any x-wind component while taxiing or taking off and landing. A nose gear airplane is like a child's bike with training wheels attached. The same applies to an airplane. It's been my experience since flying with many different nationalities that a pilot who has only flown a nose gear plane is lacking in basic x-wind flying skills. Attempting to teach a low time pilot with no airplane tail wheel training before attempting to fly a Douglas DC3 is an accident waiting to happen. Unfortunately my employer is not able to find any perspective tail wheel pilots to hire. That puts the instructor in a difficult position because he must allow the student to pilot the airplane.