As they've been on for a while, the hair dryer will soften the adhesive and more will come off the car with less work. Don't heat them till they are too hot to touch, just getthem good and warm so the adhesive gets soft, then use the dental floss. Dental floss alone will just cut the double sided foam tape in half leaving half the tape and all the adhesive on the vehicle. You will then probably need to use a good polish then wax to get rid of any shadow left on the car as the paint under these emblems has been protected by the emblem and the surrounding paint may have some "age" to it.

Take some progress pictures and show us how good a detailer you are!!!

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