Lozzo

Quiff, leather car trim was my business for many years, so trust me on this.

Get hold of some panelwipe that car bodyshops use, Do Not Use Paint Thinners!!, panelwipe is strong enough. Grab a soft clean white or red rag and use that with some panel wipe on, that should clean up what's left in the folds and grain of the leather.

Go gentle and don't scrub away at it too much or you'll start to attack the outer surface of the leather. Don't soak the leather with the panel wipe either.

Good luck