I understand the feeling, its a complex process that I am still trying to wrap my brain around. The best way to go about it is start slow, and work your way up. First I tried experimenting with just highlights and washes. Now that I have a better idea of how to do that (still trying to improve on it) I'm trying to learn shading and glazing. There is no reason to try and learn it all at once, break it down and learn each step/technique individually and then bring everything you learned together. Doing that you will see your work improve by leaps and bounds.