Bulgarian demilled training rifle M95

I have finally been able to confirm that these rifles were painted black. I had a suspicion of this as my rifle had black paint inside the dents and cracks. A fellow in a facebook group has one that has a significant amount of black paint remaining on it.

So, if I were to decide to paint this black, what type black paint should I use. I have not decided on this as I like it the way it is and the thought of painting it black doesn't exactly appeal to me but for my display purposes, it would be more accurate painted black.