>>28490991 (OP)Everytime when you replace worn brake pads with new brake pads. You should clean & then grease the brake caliper sliding pins, brake caliper and brake pad(back and sides) sliding surfaces. If theres rust between brake caliber and brake pad sliding surfaces you need use sandpaper to remove that rust first.
Use silicone grease for brake caliber sliding pins. Brake caliber grease to other mentioned parts. Never put any grease on brake pad friction material, brake disc. Dont use copper grease because it can cause galvanic corrosion issues. also dont use regular petroleum grease because it can deteriorate rubbers from brakes.