[ceviche]

I've had success with the most stubborn of hard water spots by wetting a rag with HEINZ distilled white vinegar (acetic acid if I recall my chemistry) and liberally apply and wipe, rinse away quickly and thoroughly. I had an incredible amount of stubborn water spots accumulated at my air conditioning outlet and this vinegar removed it all. I did this while the boat was on the hard and soaked a rag and wiped it on let is sit for about a minute wiped and then rinsed with clean water. I repeated this 3-4 times.

I was paranoid that it may harm the surface but it work fantastic. I actually tried it on a stainless strip that was covered in hard water spots first. My thought was that if it's safe for human consumption it must be fairly mild as an acid and should be OK. I had buffed and polished with 3m and meguiers products and several other spot removers unsuccessfully. My paint is Flag Blue Awlcraft (acrylic urethane) not Awlgrip (polyester urethane) but I believe you will have similar results with your more durable awlgrip.