I use my Dremel to sharpen. Filing is good for a quick touch-up, but too much like work if really dull. Often that is because I got into dirt or worse. Cut something at work last week and hit a bolt...:BangHead:. I usually have files and an extra chain with me if I am not going to have electric available. I probably take more metal off than needed with the Dremel, so uses up the chain a little quicker. But I hate working with a dull chain.