One other thing you can do is to fly level and pick up speed. The rudder was put on the plane as a flying surface. If you gain speed the rudder and other controls will be more effective. The minimum speed the rudder will hold the plane straight is known as (for a twin) single engine minimun control speed.

I fly the model herk and have over 1000 hrs in the full size. The rudder MUST be used on the full size to get the bird back to the runway. I demo/ed this to a student when I was an IP. He would have made a smoking hole without the rudder.

Now for the model,, cautious use of the rudder is helpful. Remember you can't feel all the back pressure the servo does. In the real bird you have direct feedback to your foot.

On my model herk I mix ail to rud. That way when I lose and engine (twice in 35 flights) and turn into the good engines I have rudder to help. (WARNING don't turn into the dead engine unless you are extremely high and have lots of airspeed)

Jim