Fluffy and Baby have their grooming sessions daily, usually after floor-time. We trim their nails once a week, taking great care not to cut the "quick" which contains the blood vessels. Baby is short-haired and requires little maintenance but the first time I combed his fur, a lot of loose hair came off! Guinea pigs also groom themselves regularly but at times they messed up and only a bath will take away the smell.
Fluffy and Baby take a wet bath (water and shampoo) once a week and more often when they "smell". They also take a dry bath (with a powdered shampoo) about twice a week. Both Baby and Fluffy are very co-operative during bathtime. They have allowed me to shampoo them thoroughly and then dry them briskly with a towel without any fuss. Wet shampoo makes them smell good but I'm afraid to use it on them too often because bathing them too often dries up the natural oils on their skin and causing them to itch and scratch. The dry bath is good but also acts as a bleach! Baby seems whiter and brighter after the dry bath. Fluffy's brown fur looks much lighter too after the dry shampoo!
Keeping the guinea pigs clean is important for their health, our health and comfort. That is also one main reason why I find it so hard to let them burrow into the beddings and would never consider an arrangement where the guinea pigs would have the chance to roll on, run and sleep with their droppings!!