I’ve brought a few old Filofaxes and leather journals back to life, and what’s worked best for me is starting with a gentle clean using saddle soap, then letting them dry completely before conditioning. For cracks or worn spots, I’ve had better luck with a leather balm or cream conditioner (like Saphir or Chamberlain’s) rather than wax alone, it soaks in more and keeps the leather flexible. If you want to even out color, a cream with pigment works great, but test it on a hidden spot first. Biggest tip is to go light and repeat over time instead of doing one heavy treatment, or it can look patchy.