I love these, and have about a dozen on my layout.
Some things I’ve noticed in restoring the ones that required a respray...
The tower’s individual components rely on conductivity between all the metal parts to supply the grounding circuit. I’ve restored several that a repaint was applied too thick, and were sold to me as ‘non-functional.’ Simple removal (or reduction) of the paint between sections remedied this.
I believe Marx’s choice not to prime was intentional for this reason. While I’d agree in nearly every instance that priming before paint is the best way to go, for this particular job, no. Giving the metal a “key” by scuffing it with fine sandpaper & insuring it’s oil free with acetone, will give the paint all the adherence it needs.
I assume this is for an indoor layout, and won’t be subjected to weather. If it is going to be outside and you want the utmost paint protection, you can run a ground wire down from the lights internally, to the common thumb screw.