Well I got my bass used, and it was in pretty awful condition (the previous owner did not look after it or even use it properly at all). 2001 model so similar deal. It was really not pretty - the neck was even kind of sticky.
So what I did was use some cleaner I have for my upright bass, and really gave it a good scrub with a cloth - all over, neck and body. I'm sure anything meant for use with wooden instruments will work just fine, as they're designed to get the dirt off, so really go for it. Use lemon oil on the fretboard and good scrub there with a toothbrush to get all the grime out (wenge is a pretty open grain wood and a lot of crap gets built up in it, but it's also quite dense and solid so you can really scrub it well). I then used some brass polish I stole from our sax player when he wasn't looking and gave the frets a good shine too - it really helped with the visual aspect.
If the frets are actually tarnished, some people here totally going to town with the frets - putting the body in a plastic bag, tying it up, putting masking tape on the fretboard leaving the frets themselves exposed, and then using brillo pads or steel wool to scrub the frets. You put the body in a plastic bag to stop little bits of steel wool getting stuck to the pickups. It's an interesting process but I think only in extreme cases would I go down that path.
After I got a ton of dirt off the instrument, I then went ahead with the wax. It had never been waxed either. So I really got into it, took a good lump of it and worked it into the wood with my hands (the heat from your hands melts the wax and really gets it to penetrate) and I left it on for an hour or so. Then I got to work with a clean fresh buffing cloth - it was hard but the wax really got into the wood and penetrated it. It really brought it to life. I've only ever used Warwick wax so I can't say about the brand you mentioned, but if it's plain old beeswax it should be ok...
So, after a total of about 4 hours the bass looked pretty good. A lot of elbow grease went into it, for sure, but tt was definitely worth the effort and became more enjoyable to play as a result.
There's nothing really quite natural oil finish basses - they look fantastic, and you really feel the connection with the wood - it feels... well, 'natural'. Nature, technology and craftsmanship to create something that helps you create music. It's just they need more care than ordinary finishes. The wood is almost 'alive' in a sense - it breathes and reacts.
But you're right, perhaps something like wrapping the pickups and body in cling film might be safer than just a bag.
