Hi, i would paint the m2 because of the frame counter, it´s far easier to paint this type than the one with glass/plastic window.
When you take it apart by unscrewing it many times the thread goes bye bye, setting it again can be problematic.
Besides that painting the rest of the camera is basically the same.
Of course it depends a lot on condition stripping chrome can produce damage even if done with extreme precaution there´s always hazard of ruining threads and other stuff, leicas are extremely precise machines and all matching parts are calculated to fit including chrome thickness.
Painting it alters radically thickness and tolerances between parts, for instance painting a lens is just hell, chrome, painted and anodized thincknesses and material behaviour are soooo different...
If the camera is not ugly don´t paint it.
Bye!