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.
This lets you both loosen or tighten the brakes, as required. Depending on the strength of the user to control the rollator, and the upward or downward incline of the surface level, brake tension can be adjusted for faster or slower movement. Control the speed of the rollator by loosening or tightening the brakes.