How to clean the interior of metal waveguides

I need to clean the interior of several waveguide segments, bends and so on, which have not been used for years. There is dust, bugs etc in them, how can I clean them?
Which products/methodology should I use in order to not damage or pollute the interior walls?
regards

What metal is on the interior surface? Aluminum, bronze, silver...?

Interesting question, I would like to know too.

What the inner dimension of the waveguide, the total length and the angle of the bend ?

To be honest I'm not totally sure about the metal composition, but I'd say brass or bronze.
I have several assemblies to clean: mainly straight segments (50 to 150mm), round bends in both planes and coax transitions; all the assemblies are for x-band (22.8mm x 10.09mm section).
regards