Only drawback is wax tends to trap dirt in with it? So maybe something with less wax, like Tru-oil?
I agree with Brian Q.....an oil finish would be preferable to wax in my opinion, less chance of gumming up the string windings over time too.
On my boards, all hardwoods, all I use is lemon oil, smells nice too! It's really all a fretted board needs, and on a fret-less if you do get a bit of string wear over time, it's easy to sand it out when it's time for a bit of maintenance.....or just leave it as it is, honest wear and tear, if it's not affecting playability.
One point worth mentioning is to avoid over oiling....it can sometimes soften the wood and frets can work loose....not so much of a problem if you glue them in, but there's two schools of thought on that one as well...! I do mine about 3-4 times a year with lemon oil....the idea is to stop the unfinished wood drying out too much and potentially cracking, although this is something I've never seen in 'real life' on a properly maintained instrument.
Hope this helps!
Beware, most lemon oil is artificial lemon & yellow coloring? Not good if your neck has binding? Plus your fretboard doesn’t need artificial colors or chemicals that can lift frets/ binding. Food grade mineral oil & pure linseed oil is best? Pure linseed is hard to find, most boiled linseed has solvents in it FYI, you don’t want solvents on your fret board? Also tung oil is for furniture, not guitars, there’s a few different petroleum solvents used as penetrators in tung oil? Better off using something recommended by the guitar manufacturers, they’ve done all the research, they know what works best?
I use organoil hard burnishing oil, a tung oil preparation.
When I visited the Kamaka ukulele factory they used Whatco Danish oil.
Generally any light finishing oil will suffice though try to minimise the use of oils that may contaminate your strings. Always buff as much of the oil off as you can and give it a bit of time in the sun to really kick off the hardening. Especially if using steel strings.
Just a couple of things I would like to mention on this subject.
Its often been suggested in the past on the forum that wax it not a good medium to use as it attracts dirt and dust. It may depend on how it is applied or the type of wax, because I have not experienced the problem in over 30 years of cleaning and treating customers fingerboards with a wax.
As part of my service, no matter what the repair, I always polish the frets and clean and treat the fingerboard. In all those years that's a lot of fingerboards getting waxed. Never a problem.
How much do I apply? Well if I say I've used the same can of teak wax 750gms in all that time might give an indication.
I recon I apply far less than a runny liquid or spray does. People that use excess treatments get charged more for their refrets due to the extra work it can create.