The actual belts need a good clean thats all, a build up of dirty n grease from your hands.
Just retract them fully, get some strong pegs/clips to keep them out, then just use a little soapy warm water and a micro fiber cloth, don't over soak them but take your time to clean all of the belt.
Dry as much as u can with another micro fiber.
Leave them fully extended to dry, may take a few days at this time of year.
Did mine late last year, work a treat now