I learned everything I know about shading and the like from my mother. (Not that I am an expert by any means) She was a painter but use to use colored pencils to sketch out a design before painting it. She was taught to paint by Jan McCraw. Jan has a great CD book on pencil techniques. http://www.ladybugcreations.com/artist.htm it is on the skill series page and is called colored pencils 101. If you click on the CD you can see the lessons inside. Some if you look in the painting section at craft stores you can find books on colored pencils as many painters do this.
On the blending stump issue...I like the harder stumps and I ONLY use the big chunky ones, not those skinny tortillions that are floppy! It's very important to sharpen your stumps to a point every time you use them and DONT try to sharpen them so the tip is round and blunt. I did a class at my lss and explained/showed the students how to sharpen my stumps but they sharpened the tips right off! I spent forever sharpening them up so they were just the way I like them!
Some people like to do their coloring and blending very dark and some very light, I think it's a preference or just a style. I tend to do the softer, lighter pressure coloring so my images are usually not as bright or bold as some others.
Kerry