temporary guitar refret

There are a couple of things you can do if you don't know which scale
you want to refret to. If you know for sure you are going to refret a
12tet instrument, you can remove the frets and make a fretless to start
with. Unless you plan to completely replace the fingerboard, this is a
step you will have to take anyway. Then, you can get some thick nylon
fishing line and tie it where the frets will be for your proposed scale.
If the line on the back of the neck bothers you, another alternative is
to give the fingerboard several really good waxings (polishing the last
one well), and glue, with very little super glue, thin brass rod that
can be found at hobby stores where you propose the frets will be. If
done just right, the "frets" will stay down, can be leveled with a file
if done very gently, but can be removed with a little force and very
little damage to the fingerboard.

--
John Starrett
"We have nothing to fear but the scary stuff."
http://www-math.cudenver.edu/~jstarret/microtone.html