What I have used for decades to remove lettering is a product called "Easy-Lift-Off". Wipe it on and let it soak for a while. Then use a brush to wipe it around the lettering, this will soften the lettering up. Wipe that off with a paper towel and reapply. Repeat this until lettering is gone, this usually takes less than ten minutes. Once all lettering is gone wash the shell with soap and water because ELO will continue to work on the paint, washing it neutralizes it.