If you were doing a already refinished guitar, you might know what kind of finish it has on it. What kind of guitar do you have? If you could research, and find out what finish it has on it, it would be a world of help. Even guitars 15-20 years old were finished with polyester. Polyester is a real pain to remove. All the strippers that I tried barely hazed the finish. You can try some over the counter strippers, you will know if it is polyester right away. If it is this type of poly, you would need to sand, or use heat. If you do either do it in a well ventilated area. The gasses off this stuff will kill you. Hope this helps, and if anyone knows a chemical stripper for polyester, please, speak up.