I have used a cleaner called 'Decasol'. May not be available Stateside but it is just a cleaner for leather car seats and can be obtained at car dealers. I should think there will be an identical stuff available where you are. I paint it on with a paint brush and leave for about 20 minutes and then wipe away with a clean cloth. It brings out the dirt without destroying the patina. I then; after it is thoroughly dry, use a saddle polish. Seems to work for me and feeds the leather without destroying the look. Lagopus.....
