chickenpicker, it IS possible to slot your own nuts without having to shell out the RIDICULOUS prices for so-called "professional" nut slotting files. For a decent set (in UK) you can expect to pay between £50 and £85 ($90 - $150), and at that price you would need to be slotting an awful lot of nuts!
Brandoni do a set for around $30 but a colleague told me that they were "best avoided for that money"......
My own set is made up from nothing more complicated than hacksaw blades. Each one is approx. 6" long. The 6th/5th/4th & 3rd string slotters are made from standard blades, carefully ground down either side to achieve the desired slot width. The 2nd/1st string slotters are made from junior hacksaw blades, again carefully ground down.
I'm afraid that the grinding process is all down to patience, trial & error when trying to achieve the correct width - but when hacksaw blades are so cheap it's not a big deal if you have to throw a couple away.
Slotting nuts is all down to patience and careful, slow workmanship anyway. Rarely can I cut all 6 slots and say "Wow - perfect" (in fact, I've NEVER had such luck!).
When you say "professional looking nut slots", that's not down to the slots - the look of the nut is down to the final finishing, shaping and polishing - you should hardly be able to SEE your string slots!
Best bet is to buy some cheapo blank nuts of eBay, make up some nut files, and... well, try it! You'll be surprised how quickly you will become confident and proficient.
