I painted my sliders with Rustoleum hammer finish. I had seen some sliders with grip tape and liked the idea, so I tweaked it a bit.
I taped off a section along the entire length of the sliders top (step) surface about 2" wide. I painted a moderate coat and, while the paint was wet, I sprinkled a texture additive that is commonly used to provide traction to painted floors, steps, etc. I allowed this coat and texture to dry a bit, then painted a top coat. I essentially painted a strip of weather tape along the top.
I gave the sliders about three coats of the hammer finish. It's supposed to be able to be applied over rust, so I figured it would make for easy touch ups in the future. A bit shiny for my taste, but effective, anyhow.
I'll post an update on how my grip along the sliders' holds up.
Pics available. I'll post if you'd like.