I haven't used any of the following, but when researching on CN, seems the consensus was that this one is possibly the best out there:
Musou Black Paint 100ml. But's it is quite expensive and also very fragile once applied.
An alternative which is not far behind, but much cheaper, is this one:
Sennelier Abstract Matt 60ml 759 Mars Black.
I would only use them for the inside/internal surfaces which are part of the light path. For outside surfaces, just use any suitable for the material paint.