Converting Harvey into a DMU

I presume the Thomas has a battery oil smoker in?

The steam is produced from distilled water.

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And that's it so far - now need to clean, prime, and paint these. Does anyone have any advice on which paints work best without chipping etc. I imagine most paints won't take too well to the polished surfaces, so any prep tips appreciated.

Use Halfords (if in UK) grey primer in a spray can first. See reviews - mostly scale modellers singing its praises.