Good ways to clean up "black stuff & staining" from powder coated MS items & bolts/ screws, post DIY mods at a Lathe heavy metal workshop?

Pic Collage: Anything anyone touches w/o washing hands has black stains all over. Only industrial workshop I have access to via a connect.

• I am a newbie with no such background and one fellow there said Collin spray.

  • Not sure if he is educated on the space but I cant imagine washing these metal parts with soap an water.

• What're the ways to do it? I will need to go there again for a few more and will come back with stained metal parts & bolts.

So, this would be a good "how to"

PS: US / UK Suggestions also welcome as long as I can source the product or translate that and its active chemical ingredient and find a local clone (in Asia).