I've dipped some blasted parts in Eastwood's blackening solution before. Do NOT let it soak, just a quick dip to darken the color of the metal a bit. Gives it that heat treated appearance.
Then, you can apply either a matte clear or RPM to preserve it.
Glass bead the part, treat it in the Eastwood blackening for a second then hand polish the piece with 0000 steel wool. The steel wool will make the piece look new and natural again.