+++ for AgX. My three Nettars shed paint flecks like Persian cats but when used within their limits, produce truly outstanding negatives, sharply defined with a slight touch of pleasing softness. I have a bottle of Tetenal black paint bought what? 15 years ago, seemingly self refilling... Clean the metal area to be painted, however. I use lighter fluid and wipe it off the metal. The paint will eventually flake again, but if done carefully, it should last a while.
Someone once told me Nettars with flaking paint were prone to flare but I've not found this to be so. With Novar lenses you should always use a lens hood anyway.
Someone else also told me they use(d) black felt markers to touch up the flaked spots. I've not tried this, but it seems sensible advice. The two someones were master photographers in their time and I respect their advice. So.
You should regularly open the back of your Nettar, turn it upside down, and give it a good tap to dislodge any paint flecks.
You may already know, if you set the lens f/stop setting on the red dot (at more or less f/11), it's the Nettar's sweet spot. Your negatives will be rock sharp.
Enjoy your Nettar, they are truly amazing cameras. Agfa like most other postwar German camera makers had it right. Someone (here I go again) once called them the Lomos of their time (1940s-1950s), but to me they are far, far better than any cheap modern plastic junk boxes...