Can't remember which Guidi calf the derbies have --- is it the matte black or the olive? --- Olive: use VSC or Reno every so often. I haven't tried Bick 4 on these but they've worked well on similar leathers.--- matte black: I had good success with Lexol. It did NOT make them shiny (what I was afraid of), but almost returned them to a newer matte black look. Anyway, congrats on your purchase.