Just did one recently. Guy wanted a buffalo horn nut and wanted the fingerboard black too.
I used Fiebing's Pro Dye. Couple coats applied with a dauber. Rubbed down with a paper towel and then wiped on a good coat of Renaissance wax to help seal it in.
I tried the Fiebing's "Leather Colors" which is water-based, and it just sat on top of the wood and came off when I wiped it. No good. I have no experience with the Stewmac stuff.
The Fiebing's Pro Dye is good stuff. I don't know about black as the ace of spades, but it definitely dyed the wood, and it penetrated very well.
On the bridge, I had the use chemical stripper to get the finish off. I also sanded it to further ensure that all the old finish was off.
This picture was the first go-around. I did end up sanding the brown area down and re-dying it. I had it all sanded down and didn't expect that the previous finish had penetrated that deeply. It was a bit of a challenge.
As you can see, it didn't get as dark as the ebony pins or the buffalo horn nut. But it's definitely black and IMO got the job done just fine.
Never heard of the dry rot problem. Hopefully won't hear about that in my lifetime
