Ash's process is fine, but not if there is not a lot of lacquer left on the leather - so beware! If the pigment is fine (thin) you could remove colour.
This is a worse case scenario of course, but its not uncommon to be cleaning pigment instead of lacquer!
Its always good to carry a can of lacquer in the van to touch up afterwards (chargeable if a lot). This prevents call backs due to pigment 'flaking off'.
If you want to play it a bit safer, use a brush to clean, it takes slightly longer but is less damaging. Personally I only use the magic sponges when restoring as this cuts it back quickly, and isnt an issue if lacquer is removed.
Good luck