My experience is flying Dash 8 200 and 300 series, some nearly 20 years old. Rudder trim only was required. If the autopilot was engaged and it was out of balance, the aeroplane would fly one wing low because the autopilot didn't have rudder control aside from the yaw damper and it would try to stop the heading wander caused by insufficient rudder trim by banking. However, although this showed up as flying with some bank, it was fixed by using rudder trim. We hand flew them a fair bit as well and I never had a need to trim aileron other than just after take-off. Obviously other's experiences are different, but I think the rudder trim is a far more important tool.