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... many of which are glass and metal...
That's not easy stuff to shoot. I know 'cos I shoot cars for a living. Often you NEED the reflection to model the surface and show it's shape properly. More so with black or dark objects.
I have lots of automotive lighting tips here and these might be useful to you, at least for the highly reflective items.
...Since I'll be making hundreds if not thousands of photographs for the museum I'd like to learn something about creating a simple lighting setup designed to minimize reflections...
You'll find that there is no simple setup that will work well for everything although a basic 2 light setup (using suitably diffused lights with lights either side of the camera) will give a relatively soft and shadowless light. You might need a third light for the basic setup behind/above the objects to give a bit of a rim light if shooting against a dark background. The fact that you have so many pieces to shoot suggests to me that you will probably have to spend a bit of time with every 'different' type of object to find a setup that works well, and then shoot as many similar items before changing setups.
...All I have at the moment is a Canon 430EX flash unit.
I suspect you won't get very far with a single speedlight but just start with the simple objects, those that are less reflective, and see how you go. I'm sure you'll learn a lot by the end of the project and I suspect you might have a few more lights by the end of it too.
Don't forget that you can potentially use other types of lights such as fluorescent lights although the colour balance will never be correct. Tungsten is an option, although possibly too hot for the museums liking and they may even damage some objects, but the colour balance should be easy to correct fully if colour balance is important (it might not be).
Cross polarisation is an option but you will loose lots of light with that setup, approx 3 stops (1.5 stops on the lights plus 1.5 stops from the PL on the lens). You won't have a hope in hell with just a couple of speedlights unless the objects are quite close or you use a high ISO which will then give you relatively poor image quality. Cross polarisation really does require powerful strobes but if you use PL gels on continuous lights then you can just use a suitably long exposure instead. I only ever use it for small objects for this reason as I don't have uber powerful strobes and I hate using high ISO's.
You can potentially light paint the objects but this is time consuming and not something I'd suggest for hundreds/thousands of items. But you would only need one light!
Maybe you've bitten off more than you can chew. That's not necessarily a bad thing. There's no better way to learn IMHO.
Good luck, have fun.