I tested on scrap timber to learn any problems.
I purchased a wood burning pen expressly for marking frets. Once I found the correct tip, it looked good. I have to say that it is a bit tedious since any wobble creates a permanent mark. A good straight edge can help. Also, I found that lightly block sanding after the frets are burned in, helps to create a crisp line. Good luck and share photos.
I agree with taffy, learning on some scrap is the best way? It takes a little to get it right. Make sure it’s hot enough before you start. I use a speed square for the fret lines, also there are specialty tips of different shapes that make the markers pop.
This is how we do it in Colorado...
Mountain peaks are major frets (3, 5, 7, 9///) Pine trees are minor frets.
That's a nice way of doing it Alan, it looks real good.
A deck screw heated with a torch makes a great fret marker... As does any other round flatish thing... :-)
I like the rustic look of wood burnt fret markers....they don't have to be perfect. Just adds to the look