arbud,
Welcome!
I thought maybe you were going to tell us a better way to do it!
I have tried everything from sand paper, to rat tail file, to rasp, to bondo file, to die grinder. The die grinder worked the fastest and if you know how to operate one, it did the job the smoothest. After it is roughed in with a die grinder, you could wrap some emory cloth around a dowel rod and work it straight again, but I wouldn't even mess around with any 00 grits. Go for the 80 grit or some such, since you can always smooth it further with finer grit. The synthetic just doesn't cut real easy.