Six frets done.  The first one was the ugliest, after the third one I had a pattern that worked the rest of the way up the neck: 30 seconds of heat applied with a 40W soldering iron, then start pulling at one end with my special cutters.
Project: Tobias Defret
March 3-5, 2006

When I got this bass in 2001, my first impression was, "This will make a great fretless!" I'm glad I was right - there's no turning back . This is my first defretting project. When I do it again I will change a couple steps, but I am very happy with these results.

Udate 3/08: After trying DR Black Beauties and D'Addario Chrome flatwounds, I grabbed an old set of Fender 7150Ms that were already used, but they sound great on this. I am now using 7150s on this bass and my G&L SB-2 Tribute.
Speaking of special cutters, here you see my 99 cent end cutters.  I used a file to smooth the front side so they can get under the fret.

I'll use the cutters again to trim the maple strips down before sanding.
All done with the removing process, now it's time to widen the slots so I can fit maple strips into them.
Finished!
I used a dovetail saw to widen the slots.  That gave me roughly 1/32" to fill with wood, rather than trying to stuff something into the narrow grooves.  The cardboard took some damage during this step.
Cutting wood strips to fit has taken some trial and error, but  once I get them just right they get glued in.  20 more strips to glue, then I'll let it sit overnight.
Sanding started with the base of a block plane to hold the paper.  After a few strokes I switched to a 1/3 sheet sanding block that came with a drywall tool kit. That gave me a spongy backer which conformed to the 16" radius of the neck.
Things to learn from me:

Use a tool that will cut a clean, consistent kerf for every slot.  Or fill the original slots with very thin veneer.

Three thin coats of polyurethane is a good start but it doesn't make a difference in the long run. Pros use many coats of polyurethane or epoxy for a durable, glossy finish.

Protect
everything that you do not want to cut or sanded.

Unless you want to buy a new neck or replace the fretboard, there's no going back!
Long sanding strokes removed the black finish from theE and G tuners.  the bridge pickup also took some minor damage before I put masking tape on it.  That's why I did this on an inexpensive instrument! 
Sanded and ready for a polyurethane finish.  This is the 19th fret.  The saw got a bit out of kerf and the maple strip broke off below the surface.  It gets the ugly fret award.  I filled it with some glue and sawdust to get it mostly smooth.
Hosted by www.Geocities.ws

1