Short-haired guinea pigs groom themselves, usually with some assistance from their GP friends. All owners need to do is clean the grease gland, (see Guinea Pig Grooming) provide a regular bath, and give them a brief brush every now and then - always in the direction in which the hair grows.
Short-haired Guinea Pigs groom themselves
If you notice a guinea pig's fur is looking untidy, check for health problems. If there's no underlying problem, you might want to increase the frequency of brushing, to keep them looking in top condition.