Set the skew (tilt) exactly as per the spec and leave it alone.
Make sure you have ZERO line of sight issues.
Next make sure your mount is true, plumb and level on all sides.
If the above is done correctly, then the elevation should be exactly per spec also.
Then only adjust the azimuth as needed, allowing a few seconds between each adjustment for the signal to level out. Use a marker to note where you started.