Going to assume you are referring to the ESB / SE helmet. leather by Model Master is a good color for it. For the darker spots, you can use it straight from the bottle and apply with a paint brush. For the lighter weathered areas, you can dilute it.
No problem bud! Check out the Celebration IV folder underneath the boba fett references tab in the media section. a lot of great shots of the ESB helmet but just keep in mind that it has been beat up over the years. So always look back at ESB era gallery images to see what is and isn't present.