I would recommend using a solvent to clean out the dust and then follow with a steam cleaning...any engine overhaul shop should be able to direct to the correct resources, if you don't know of them already.
The steam will get rid of any remaining dust and solvent. The metal should then be squeaky clean.
Finish with an oil-based clear polyurethane.

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"With malice toward none, with charity for all, with firmness in the right as God gives us to see the right, let us strive on to finish the work we are in, to bind up the nation's wounds, to care for him who shall have borne the battle and for his widow and his orphan, to do all which may achieve and cherish a just and lasting peace among ourselves and with all nations."
- Abraham Lincoln, 1865
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