Ryan, I would go with a medium grade claybar (http://www.detailedimage.com/DI-Acce...P376/100-g-S2/) and some really good slippery claybar lube (http://www.detailedimage.com/Dodo-Ju...326/250-ml-S1/) or a really good quick detailer (http://www.detailedimage.com/Chemica...P220/16-oz-S1/).
If you go the cheaper (clay and detailer) then make sure you spray the body parts down until soaking wet AND the claybar in your hand (use a glove) then start claying the car. wow, that all sounded.....umm...nevermind. Make sure you keep the car wet with the detailer AND the bar wet. It should glide across the body no matter how much you push the bar. If you feel the bar start to snag or drag, you aren't using enough detailer or lube. Work in 2x2 or 3x3 sections and spray clay spray clay(use a side to side, then up and down motion), then move onto next section.
If your overspray is bad, like you said, you are looking at doing the car at a bare minimum of 2 times. Sorry to tell you that but if you want it all off your gonna have to get in there and do it right. When it is done, you should be able to take your hand and lightly run it across your paint till it feels like butter.
My suggestion:
Medium Grade Clay Bar
Chemical Guys Synthetic Quick Detailer
Latex gloves
FYI: If you don't want to wait for shipping, you can get just about all of this at Autozone/Checker/Pepboys/etc... Get the Meguier's Claybar and Meguier's Ultimate Detailer.