Adjust the tilt/range to just see the very top of the buildup
The problem with that technique is the radar may not "see" the actual top of the CB because there is very little moisture up there. That is why turning the Gain switch to MAX instead of AUTO may possibly give you a tiny return but not always. Radar interpretation is indeed an art of its own and you can obtain plenty of practice by observing CB visually then compare what you see outside with the radar picture.