Ebbtide,
You can use flat, triangular, round(chainsaw) files. Any file will work.
Do some experimenting on scraps of metal to figure out which file gives certain patterns.
------------------
If a man can keep alert and imaginative, an error is a possibility, a chance at something new; to him, wandering and wondering are a part of the same process. He is most mistaken, most in error, whenever he quits exploring.
William Least Heat Moon