I've got an old ATK 305 from the 90s that I bought used and it arrived with a few problems. First I had buzz on the first fret, so I replaced the nut myself. So I managed to fix the buzz at the first fret, which is awesome. Because I fixed the buzz at the first fret, I decided to start lowering the action to more of my style. I followed an Ibanez manual that said when holding down the first fret, the neck relief should be between 0.3 and 0.5 mm. And it just so happens on the bass side the lowest I could get was .6, and lowest on the treble side I could get was about .5 without excessive buzzing. even at this amount of neck relief I still have some intermittent buzzing. I did some thinking, and based on my VERY limited knowledge of guitars, that the frets are probably not level. What do I need to know/ what tools do I need, before attempting to level my frets? However I am not 100% sure that is the culprit. The strings on the bass currently are long-scale, and because this is a string through bass, this causes the tapered part of some of the strings to sit inside the nut, my understanding is this is not ideal, so I have ordered some super long scale strings to see if this helps. The bass usually ships with a .125 B string I'm guessing, but when I got it, it had a .130. From what I've read a thicker string will actually rattle less, but I've also considered that maybe the .130 puts too much tension on the neck. I'm a beginner at working on my own gear, and while I do have plenty of sandpaper and files, I am not sure what other tools I need to attempt to level these frets. PLEASE let me know if I am mistaken about anything here in the post! Thank you folks!