Has the boom grip material worn off? maybe a rewrapping is needed.
I am curious about why you would want to have "rough" booms. Roughness on the grip usually seems to cause a lot of soreness on the hands. If the booms are really slippery, caused by too much suntan lotion for example, try washing them with soap and warm water. The sand paper will work too, but you won't want to rough them up too much. I have one boom that is 5 yr old, and it just beginning to get comfortable and doesn't irritate my hands as much as when new. Hope you aren't "gripping" too hard with the hands.