Using a kitchen mixer can be messy. The folks at CHOW offer a couple of tips in this video to help you get the job done and keep your kitchen benches (and your clothes) clean at the same time. The first involves a kitchen towel, and the second a sheet of wax paper.
For standing kitchen mixers, drape a tea towel or a kitchen towel over the mixer while you run it to keep dust, flour, or splattering liquid from getting all over your benches. For hand-held mixers, a sheet of wax paper between the mixer body and the beater attachments will do the trick. Make sure the beaters have enough room to spin freely without getting caught in the wax paper.
I can definitely vouch for the second tip. Operating a hand mixer can be treacherous, especially if you're not using the right mixing bowl or have a lot of dry ingredients.
Mess-Free Mixing [CHOW]