When the clip broke off of my Clip + I used a fingernail smoothing file after clipping off the big bits with wire cutters. Not a normal two sided file, this is one that is used to smooth the tops of fingernails, to get ridges out. It is basically gradually smoother sandpaper on a stick, I think mine has 4 different textures. By the time I got to the smoothest selection the back of mine was smooth as a baby's bottom.
OK, fine, not that smooth, but it did look pretty darn good, and I think the fingernail smoother cost me all of $2 at Walmart.