Fingerprint powder -- how to remove?

Factual Questions
1

Not from my fingers, sillies! It is on the outside of a window, on white paint. It has left a kind of gray area. What would be best for removing it without taking off the paint?

(Yes, we had a break-in. Not bad, as those things go, definitely amateurs. That, or the beer they stole affected their judgement.)

2

This page suggests either using a commercially available product, or shaving cream.

3

Thanks.

Not sure why they suggest shaving cream as a substitute, but it can’t hurt to try it before buying something from that manufacturer.