discoulartionsAre you talking discolouration or black marks?
Quality stuff that!This was recommended to me for cleaning up your mechs...
https://www.ebay.co.uk/itm/Peek-Pol...var=512758082643&_trksid=p2057872.m2749.l2649
It's very good if a bit messy.
For threads I use Isopropyl Alcohol with an old toothbrush.