A few questions.
1) What type of tree are these branches from? If you're not sure, DON'T use them.
2) Why would you want to paint them? What's wrong with the natural wood look?
If you paint them using a high gloss paint, the reptiles probably will not use them. They won't be able to grip it well enough.
Seriously, if you're going to put branches in, go "au naturel".