I have cut nut slots with three types of implement. I have not used expensive or cheap nut purpose made nut files. From what I read about the purpose built nut files the cheap ones are (a) only really cheap compared to expensive nut files, and (b) terrible. From what I read, the high quality, expensive nut files are bliss to use. The only drawback I have heard about them (other than lightness in the wallet after purchase) is that it's easy to cut too deeply. Even that may not be a problem since it contributes to the building of character.

I have used home-serrated feeler gauges, torch cleaners; and cheap, small files sold in sets. I have at least three sets of the small cheap files. My main difficulty with them is that they appear to require skill to get good outcomes. I have no skill and not much aptitude. Perhaps for that reason, I rarely use them for anything let alone nuts.

Meanwhile the feeler gauges have worked reasonably well on guitars and the torch cleaners have worked quite well on basses with out much need for skill. In both cases they are slow. The one advantage to slow is that I have only once cut too deeply. The bad news is that my wife has noticed no noticeable improvement in my character.