Tiny rust spots from nearby grinders
Wait until the coating cures a bit, then wash/soak with a diluted mixture of oxalic acid. You can obtain oxalic acid crystals in a hardware or paint store. Oxalic is also found in many abrasive scouring cleansers (dont rub!) : Bartenders Friend, Zud, and many "teak brighteners'', etc. Oxalic wont harm Awlgrip, gelcoat, etc.
Caution: wear gloves and goggles as oxalic will rapidly absorb through your skin and harm your kidneys.