How to deal with reflections?

Hi there,

I recently took some pics of some cars in a rally but was faced with a lot of glare and reflections upon the cars from the clouds and sky. It wasn't a bright day, and overcast at the best of times but I was wondering if i could have done something different to create a better effect.

An example of my shots is below;

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Use a polariser, that will cut down glares and reflections. It will also improve colours and contrast.