Given the oiliness and density of Ipe, I figured Stainless Steel screws would work best for the deck. Here is a trick I learned from my old instructor David Upfill-Brown for polishing screws:
Chuck the screw directly into the drill press. DON'T OVER-TIGHTEN THE CHUCK! Simply hand-tightening the chuck should be enough to hold the screw in.
With the drill press running, lightly press the screw head down onto a piece of adhesive-backed sandpaper for two or three seconds.
Remove the screw, and voila - shiny new screw head! The screw on the left was left "as-is"- the one on the right is freshly polished.