> Thanks for advice. Have been trying soft soap, water and Scotch Brite.
> Seen very little progress. Epoxy still whitish, although it might have
> changed a bit.

You may have to be more aggressive and use sandpaper. Note that the sanded surface will also be whitish until you apply more epoxy.

> Any safety precautions? Can I go for a long trip?

Blush does not affect the strength.