Yep, I read that ‘non-permanent’ statement as well, which is rather confusing given the listed applications – after all, what good is a non-permanent paint for that kind of stuff (it’s not as if anyone is thinking of temporarily dressing up their camera for Halloween or something)?! Strange.
I can’t really help with the question but I thought, I’d out myself for also having interest in lens repairs. I did smear some helicoils and clean aperture blades of some vintage lenses (in the last month I serviced a Minolta 55/1.7 a Mamiya 300/5.6 and a Tokina 90/2.5).
I’m not a pro, but I find it really rewarding, bringing these old lenses back to life.
I did note the marker mentioned by @difrkaguilar as it my be also usefull for my needs.