Thanks, Julie (and I notice I mistakenly attributed the BLO tip to Steve rather than yourself, sorry). I'm considering just remaking the only piece with wax at this stage...might be easier than going to all that trouble. It's just a big rectangle with some edge routing, so it wouldn't take long.
That's a huge relief! I was thinking of all the work you would have ahead of you if you had to remove the wax from everything. The problem with wax is you never know if you got it all off until you try to apply a coating on top of it.
Maybe you can do some research on how to reduce the tung oil to the point it's almost gone. I looked into this further and read mineral spirits might work too. Again, I don't know. I last worked with tung oil over 20 years ago but abandoned it because I found BLO and shellac to be the better option.
Since you aren't trying to completely remove the tung oil, and all you need to do is get rid of the layer that won't cure, you may be able to "dial back" the coating chemically and move forward from there. I believe this will work.
If you like the grain pop, just coat it with dewaxed shellac and never look back.
If you want more grain pop, stick with tung oil but rub it in vigorously and wipe it clean before applying dewaxed shellac. The idea is to let it soak in and then wipe it off (wet) like you would wax from your car. But don't wait for it to dry!
This is a guitar neck I did with BLO, dewaxed shellac and Behlen's instrument lacquer
The maple isn't bright white, like some like it, but the BLO certainly made it pop. Over time, the BLO and shellac will yellow somewhat but I doubt you will see that much with walnut.