Depends what you class as 'ghosting"? If it's the glue residue, then tar n glue remover for sure (tardis by auto smart is excellent for this type of job). If it's just the outline of where the lettering use to be, then it depends how weathered the paintwork is? I'm not surprised T-cut didn't do the job, has as much cut as a wooden spoon! I'd machine polish it using a DA, you'll do it in half the time and will achieve a much better finish.