You could try the Cinematic mode. It's purpose is to dampen down the movements for video. Keep in mind that it also increases stopping distance so be ready with the cancel button on the RC. If you need slower movements there is always Tripod mode.
That helps. A few extra tricks are sitting down when flying. Use the pinch method for the sticks. Sometimes I have to over yaw a bit and then let off a bit to find the right yaw speed. Distance to subject matter creates a scale that affects yaw speed. Meaning closer or bigger objects need slower yaw movement more often. This also means zoom if on m2z. And practice. Happy flying!
If the above modes are not enough, you can adjust the stick sensitivity in Go 4 but that will change it for all flying, not just when you are capturing video.