I find these tools very useful in alot of ways. Here is just one way you can use these to to add some detail into a design. I started off with a simple orb, not really that shaded or anything.
Make your way over and select the burn tool and set the brush size to one or two pixels. Now start to draw fine wavey lines or I like to just call them veins. Do it with both of the tools, burn and dodge. Now set your tools to a bigger brush size and start shading the sides and center of the orb.
It is looking kind of rough right now, but to soften it up you can add some gradient shines and reflections inside. Then just use your creative juices from here and create some rad art with this technique. This is what I ended up with.
More Tutorials: 
