alt-reality asked: All that makes sense for filing the ends of the frets. You mentioned leveling the frets - any secrets for this?
The first step to leveling your frets is to level your fretboard. Then you need to cut your slots consistently. The slots can introduce errors in a few ways:
First: by not being deep enough.
Second: by being too tight; making the frets seat inconsistently.
Third: having sharp edges on the slots. The tang of the fret connects to the rest of the fret with a slight fillet— this curve usually just compresses the sharp edge on the fret slot, but it doesn’t always do this consistently. I use a triangular file to break the edges. This bevel also reduces tearout when refretting.
Now seat the frets: ideally, after that work with the fretboard, they will be already level. Best of all, they’ll still have the crown from the factory die so you will only need to dress the edges. Lay a straight-edge over the frets at each string position to see if you’re already done.
If not: use a fretboard block with ~120-grit sandpaper or a long metal file to skim the top. You want to stop as soon as all of the frets are touched by the leveling block. Smooth the frets with a flat sharpening stone— this plane will be the final surface for the frets.
Different amounts of material will be removed from each fret, so at this point you need to reshape the tops. Run a permanent marker over the top of each fret, then round the edges of the fret, leaving a thin stripe down the middle untouched.