Is there a painters trick to spray paint a hollow rod on all sides at
Once. Possibly suspending it on a string from a tree branch?

Tie a small string or wire to a nail or small piece of wood. Run string or wire through tubing and suspend the tubing. Twist the tubing such that you are twisting the string. Let go of the tubing and spray as the tubing spins.

Thank you so much

PS

You do know that you can pruchase different colored plastic sleeves that fit over shower curtian rods don't you?