What do you suggest for waxing leather bellows, and polishing finished wood?

I've read a bunch of threads on here, but I've also seen some contradictory information, and I can't quite seem to wrap my head around the problem.

I get that using silicone based furniture polish is bad for pretty much any kind of finish. I understand that some kinds of leather conditioners are good for leather, but bad for cloth stitching. I've read that some kinds (or all kinds?) of metal polishes damage wood fibers, causing screws to come loose.

Is there something generically safe? Beeswax or paraffin wax?

(Alternatively, can anyone suggest an authoritative resource, a book, a journal, or a conservation website?)

Thanks, everyone.