The brush that comes with the Mr. Clean Pro series (car wash kit) works great on that area. It also works good between the tires and mud guards. I bought the kit didn't like it, they (Sams Wholesale Club) said I could keep the brush.
Couldn't find a picture of the brush on the internet, it's like a "loop shaped brush with bottle brush bristles and a slightly curved handle"
I saw a similar brush near the cleaning products in an auto parts store.
Couldn't find a picture of the brush on the internet, it's like a "loop shaped brush with bottle brush bristles and a slightly curved handle"
I saw a similar brush near the cleaning products in an auto parts store.