I was doing a little work on an Industar-69 lens this evening. As part of a quick servicing job, I thought I'd clean it up externally too, as it was extremely dirty. Normally, I would clean mechanical parts and external surfaces with warm water and washing up liquid, and a soft-bristled tooth-brush. This time, stupidly, I used a cotton bud and a very small amount of 99.9% isopropyl alcohol. The focus distance markings on the Industar-69 are painted, and they started to come off while I was cleaning. Also, some of the "shine" appears to have disappeared from the barrel.
It's no big deal - the lens was super-cheap, and not in great condition anyway, so nothing lost... But I want to avoid this happening in future with better lenses.
So... my question: What are the most suitable solutions for cleaning dirty metal and plastic lens barrels with painted (but not engraved) markings? Am I right to continue using water and washing up liquid, or are there better choices?
Thanks in advance