I drybrush a sliver or aluminum color, for larger patches of wear. I'll use a fine brush and thinned paint or ink, for smaller flakes or spots of wear.
I use acrylics, eg, Tamiya's flat aluminum, and enamels, like Model Master or Testor enamels. They absolutely work.
I tried the salt technique to beat up the finish on a Zero, but it was more effort than I felt necessary.