This is caused by the solvent removing the lubricant from the metal.
To "restore" it, just apply a thin coat of CLP Breakfree to the parts and wipe off the excess.
This will also build a thin layer of lube and Teflon that will protect the rifle.

This is best done with the squeeze bottle of CLP Breakfree, not the spray can. The spray can puts out a large slug of liquid, not a spray mist. That's just too much and makes a dripping mess.
Personally, I put drops of CLP on a clean soft old toothbrush and gently "scrub" all surfaces.
This leaves a thin coating that you usually don't have to wipe off at all.