Well, I never know the name other than a blender.
You can make your own using paper towels. I like blending with paper towels for large areas.
I did purchase a plastic blender from the art store. It works okay but the colorless blender is better.
Color blenders makes color pencils darker(including crayolas color pencils)
The larger the plastic blender the more $$ it cost, this is why I purchased the colorless blender. You have woodless and pencil type.
Try using an ebony and woodless pencils. They are nice. Plus the electric eraser is cool tool. (great for small highlights and hard to reach places. )
Speaking of pastels, woodless graphite is simular and less messy.