People often ask how to clean their needle-felted artwork. Most likely, your felted piece will be placed on a shelf or table, and admired without much handling. In this case, dust will be your main enemy. In an ideal situation, the wool sculpture would be placed in a glass dome or box, but if this isn't a possibility, the easiest way to clean off the sculpture would be to use "canned air"...the kind used to clean off key boards and other technologies. Hold the can about and foot away from the sculpture, and let the air clean your sculpture for you.
Sticky fingers or dirty hands can leave residue, but no more so than they would on a wool sweater or jacket. I always recommend careful handling, but if someone does pick-up your felted artwork, leaving behind food or grime, try the canned air technique first. If that doesn't work, use a damp wash cloth, perhaps with a bit of clear dish or hand soap if needed, and gently dab the area. Do not scrub hard, and do not put it in the washing machine. Wire armatures are inside of many of my felted art pieces, and washing machines would bend and twist these out of shape. The agitation plus soap and water would also felt the pieces even further, shrinking it, and possibly deforming small details of the piece.