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.
There are four basic styles of brake controllers. The first style is a timing activated brake controller. This control works with your brake switch to activate the trailer brakes at a predetermined amperage output. It can be mounted from anywhere and generally will be used for a short hauls, or a low weight capacity trailer.