I must admit, I still try and keep my cars clean. I've always resorted to 3M adhesive remover to get off the rubber marks which takes your wax off and isn't very clear bra friendly.
Then someone turned me on to Mother's R3 which works really well in getting the rubber marks AND bugs off. Below is a short video of me getting off a 5 month old rubber mark. Sorry for the weird noise
No one local had it...got mine from Amazon.com