I don't know that I get "awesome" results, but I'm pretty happy with the ones I get. I start by lightly coloring in the pants entirely with the lightest color. I blend that out so it's smooth. I'll then go in with my darkest color and pencil in the areas that are shadowed. I usually go fairly heavily here and then blend from the darkest shadow to the lightest. I'll then go back in with my mid-tone and hit areas that I want darker, but not shadowed. Occasionally, after all that, I'll go back with my lightest tone fairly heavily over my highlights and then blend out.
Now these are dragons, not denim, but they're a good example of what I'm talking about. The top dragon is shaded out with 3 tones of yellow and orange, while the bottom dragon is actually shaded out with 3 tones of orange and red, plus an additional layer of Burnt Umber.
It really isn't as much work as it sounds.
Normally, when I'm working on an image, I'll start by completely coloring it with all my light tones. When I'm ready to pull out my baby oil, then I start working on my shading.
Keep in mind that everyone's technique and style varies. Try different things until you figure out what works best for you!