If you have steady hands use a single edge razor blade .... Grip the blade between the thumb & index fingers of both hands, center the blade, rest the heel of you hand on the car to help steady your self & take small shaving cuts off the top of the run... If you take an aggressive cut it may dig to deep so go slow... Al your want to do is get it close, that last little bit will sand out... Practice helps but ya gotta learn sometime & today is your day... Shaving is best done the day after you spray, the longer you wait the harder it gets...

FWIW I use the blade straight but I use a layer of masking tape around the corner at each end of the blade...
My buddy likes to put a slight bend in the middle of the blade so he has less blade close to the paint & better control of the cut...