The warmest sound of the string oscillation you can get is from acoustic guitar.
Acoustic guitars have body, resonant box. Oscillation of strings resonate inside of guitar hollow body and produce sound, the sound of guitar that we hear.
The important part of that sound production is dedicate to the frets, the metal bars on guitar neck. When you press string on fret, and fret is filed down you can hear buzzing sound. Also, frets from time to time gets filed down because of string sliding on to it. In that case, you need to change them with new.
The material of frets is stainless steel metal. You can buy the long wire or 25 peaces of frets in box.
When you stat to remove old frets most important is to don't damage fret board. You will tear apart some wood underneath the frets itself, but don't bother about that. To fill that gaps mix wood glue with fret board dust. Fill the gaps and sand it when it cures. Also, use scraper and clean gaps in fret board from old glue and debris.
There is a two types of guitar neck. With and without bindings. If you have binding, the white edge, like i do, you need to trim fret wire to exact size. To do that you will need to file it down so fret wire will sit down on binding without cracking it.
When you cut down all wires you need to slightly bend them. There is a fretting jig, the special tool, but i like to do it with rubber hammer. The goal is to insert one side of wire and hammer it with two easy strokes. Than hammer the other side. You will end up with gap in center of the fret and that is good. Because fret wire have metal teeth and that metal teeth's needs to stuck inside of fret board. Also, you can glue the bastard down, if the hole is wider and fret pops out. On the end, when you are sure that frets are in right position, hammer the middle and go to the next one.
Bending fret wire
Insert wire in gap
Hammer one side
Than the other side
Finally, hammer the middle of fret wire
You will end up like this. When the glue is cured cut the excess of wire much as you can with hand clippers. The rest of metal you must file down with file or sandpaper.
I use metal box with glued sandpaper on to it. Its easy'er to hold down the box and leveling all frets on one side of neck with one stroke.
On the end, goal of sanding is to make it smooth as possible, so when playing, fast sliding will not catch hand and hurt guitarist.