RE: trimming surfaces in flight?
That's true for elevator, but if you're pulling a roll at low speed you could be rolling rapidly at high speed.
When you maiden a model try a very short hop first. Correct aileron if it tracks straight but rolls on lift-off. Correct rudder if it taxis straight but then veers sharply and rolls when the wheels break away from earth. Once you have that trimmed, work on the elevator in flight.