Happened to me last fall, I feel your pain, and what a pain it is.
Acetone with clean rag will do the trick. Use a clean spot on rag each time you work on the line paint. Make sure to use plenty of acetone on rag. Wear latex gloves- acetone is nasty on the hands.
And please, do this in a well ventilated area, preferably outside. This is for your health and from keeping your garage from blowing up!
Follow with a wash and rinse and a coat VRT or undercarriage spray.
Keep us posted.