I can answer that for Miles if you dont mind a woman doing it
You'll need a round needle file and either a few grades of wet or dry sand paper or some nylon line and some grinding paste (the sort used for fixing car engine valves). First file the edges of the slot with the needle file, you should aim to just round off all the edges that the wishbone will come into contact with, there's no need to go mad and create new side slots. Then use the wet or dry sand paper or the line and grinding paste to polish the surface of the slot; actually the grinding paste is a lot easier than the sandpaper and only takes a few seconds
