If the rust spots are evenly spaced, you can use surface stitches to cover them. Good stitches might be Smyrna cross stitch, satin-stitch heart, queen stitch, satin stitch lozenges/triangles, palestrina knots, etc. If the spots are not evenly spaced, balance the design by adding extra stitches between the spots.
Fortunately, most states require drivers to equip their trailers with brakes and devices known as brake controllers. When a driver presses on the brake pedal in his truck, the brake controller lets the trailer's brake system know how much braking power is needed to stop the trailer.
The brake controller is typically installed in the vehicle's driving compartment by running an electrical line from the trailer to the trailer wiring connector. Most require the user to adjust brake gain (braking intesnsity) to compensate for varying trailer load. If your vehicle came from the factory with a Class III or better towing hitch installed, chances are that it has a quick plug under the dash for a brake controller.