Re: Nut Problem
Valve lapping compound is the quickest and cheapest method for deepening slots. Take a string that corresponds to the slot, you can even use plain ones. Put some compound into the slot with a needle and start flossing. It will cut very quickly. It can be a mess though so try to be careful.
It is not the best btw, because it might stain the nut or too much pressure might embed the compound into the nut and it will rust and possible ruin your strings. Bone is less suspectible to this if it's not porous too much. Again, go slow. Polymers usually don't stain, bone does a little. Soak it in naphta over night.
This is probably the simplest way as resources go, because lapping compounds go for 2-3 USD and you can get at any auto parts store. When I started doing repair work I made at least 10 nuts this way and it works. You can use a jigsaw to hold the string. Put some solder on the ends of thinner strings to build some material to hold on.