Have you tried the plain ol Bug and Tar remover spray? There's several companies that make it- you spray it on, let it sit for a few minutes then rub it off with something like terrycloth - then go back over it with detail spray... But I use that stuff to get off any kind of bird or insect droppings. The worst around here are those brown fly eggs. They look like little flat round brown spots and you absolutely cannot pick them off but this stuff takes them right off. It's worth a try before you pull out the big guns and start sanding and such- if it's organic- bug, bird, tar- this stuff will take it off. You can pick it up at any old auto part store.
Pype Bomb Axle-Backs, JLT CAI, SCT Tuner w/Bama tuning, BMR Strut Tower Brace, CDC Classic Chin Spoiler, Black Hood Pins, Black Shorty antenna, Tru-Billet Black Anodized GT engraved Fuel Door, Black Lemans Stripes, Black Rocker Stripes, Brushed Aluminum finish dash and vents, Stack Racing pedals, Charcoal Black Leather Interior, Gloss Black Bullitt Motorsport Wheels, Nitto 555 tires, staggered set up (9/10), 35% tint, Shaker 1000 Stereo with Kicker Upgrades, Ultra Violet footwell, license plate and dome lighting