You have to be careful with paste wax - make sure it has no abrasives in it and that it is PH neutral. Renaissance Wax is a gentle wax.
I started using Meguiar's Gold Class Carnauba Plus Paste Wax for the exterior of the Glock slide. I called Meguiar's and spoke to a customer service rep he verified that it is PH neutral and has no abrasives in it. Meguiar's Gold Class Carnauba Plus Paste Wax is also fairly oily.
I waxed the slide on my G34 and I like it. It is easier to cycle the slide than if it had a light coat of oil on it. And it's more protected than if the slide were wiped completely dry and my slide has a fairly hydrophobic coating on top of the gun's finish.
If I'm not going shooting for a while, I'll put another coat of wax on it.
Here's a picture of my Glock 17L with a few coats of Meguiar's Gold Class on it.
It's obvioulsy not going to shine like a gun with a deep blue finish. but here it is anyway: