For my colored pencil paintings, I use Prismacolor brand pencils. This brand not only has high pigment content, but also has a wax binder that is very soft allowing for easy blending.
I use only manual sharpeners for my pencils. Some time ago, I discovered that if wax builds up on the blades, the effect is the same as a very dull sharpener. The waxy blades break the leads and crack the wood casement.
In order to reduce wax build up, I keep a rather stiff toothbrush on my drawing table. Each time I empty the sharpener, I brush the blades with the toothbrush. This helps keep the wax from building up on the blades. Periodically, I also rinse the blades in warm to hot water in order to remove all wax build up.
