Once you wash it clean, put a wax on it to keep it from chalking for 3-6 months. You can use an RV-specific product like Protect-All Roof Coat, or a plain old floor wax such as Mop n Glo.
Former owner of 2004 American Tradition and several other RVs
Home is in the Ocala Nat'l Forest near Ocala, FL
Summers in Black Mountain, NC