I always have used in flight tuning for my two copters, it's the quick and easy way to tune them up for great flights! I don't have the DX8, however a few friends have them at the field where I fly, is there an AUX 3 channel on there you could use for the tuning while in the air?
When I set mine up I moved the gains up until the "shakes" started (you will know the shakes when you see them), then backed it off slowly untill it was very solid and had sharp reactions to the controller stick movement, after that I did not touch them again, they are rock solid now!