Pull it right out. Persil in a bucket of water and a nail brush. Works a treat
Im trying this tonight as my belts are shittied up to hell.Pull seatbelt fully out.
Place seatbelt outside of the car.
Close car door on said seatbelt.
Jet wash it. Works a treat.
What about jaming the seat belts in the door.. and just taking the whole car through an automated car wash?