Signing on the print

I'm printing on Red River Baryta paper, and mounting on ACM for a frameless image. The bulk of our images are night sky or dark foreground, so signing with the lovely Pigma Micron pens doesn't work. We do use those for anything with a light foreground.

We've been using acrylic paint markers, but it's easy to smear that paint, and the price of 24" baryta paper is such that it adds up.

I've seen the Pentel Sunburst Metallic pens mentioned, but gel ink seems even more likely to smear than acrylic paint markers.

Does anybody know if the silver welders pencils are a good bet? Or a white carpenter's pencil?