How do you clean exterior rubber on your car?

Use silicone on a rag and wipe it down.
I use armour-all and a rag on the rubber trim and it works great.

Use a product called F21 from turtle wax it works great..........

The Turtle Wax F21 Super Protectant shines better and lasts longer than the competition. It renews surfaces while restoring pride and turning heads. F21 is a product of choice for the car enthusiast who wants a long lasting shine, and protection that endures the elements-without the greasy residue.

The key to F21's performance is the revolutionary Nanotechnology, which protects against the sun's harmful rays. This technological advancement maximizes product performance at the molecular level. F21 prevents fading dashboards or worn-out seats, while also restoring washed out surfaces and protecting them from future damage. With its Sun-Stop® technology, F21 provides the highest level of UVA/UVB protection for leather, vinyl, rubber and plastic surfaces to prevent drying, cracking and fading.