I’ve used Furniture Clinic products. Very good. They have videos of how to do repairs and their kits are good too. I sent a sample of leather to them for a colour match.
The process is basically similar to repairing paint defects on bodywork.
They can supply an airbrush as a part of a kit for minor repairs. Don’t forget the final sealer coat that protects the colour coat. It extends the life.
Think a bit about the finish though. Is your leather matt/satin/gloss? The final sealer comes in choices of each. Test on a less visible area.
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