Sorry, I won't be much help for the inside, because I don't know if this would be ok inside.
I'm getting my dragon this coming Saturday, so a made sure that I did this a few months earlier.
I painted the outside of my wooden vivarium with white paint, undercoat/primer with a top coat (Gloss)
It was the Dulux Brand. I'm not any expert with this stuff, but all I had to know if it was non toxic. I did this because it was second hand and it made it look newer and nicer.
However, for the inside, I'm not too sure if it would be ok because the beardie might scratch off the paint (with the type I used on the outside). But again, I'm no expert.
Hope I helped