Slider bolts, caliper carriers and disc guards
The caliper carrier on single-piston calipers can be removed, cleaned and painted with a high temperature or suitable caliper paint. It’s usually secured to the back of the upright with a couple of bolts, which should be tight.
On single-piston calipers, make sure the slider bolts are clean and free to move. Clean the metal surface of the slider bolt with emery paper. Apply a suitable grease that doesn’t erode the rubber dust covers.
The brake disc guard that prevents road dirt contaminating the back of the brake disc can become heavily corroded, so it may be good opportunity to clean and paint it. This will also mean the brake disc has to be removed.