Kremer Pigments, for pure loose powder, it is not expensive about 10 bucks, mix with a couple drops of mineral or neatsfoot oil to about a half a teaspoon, you don’t need much.

The easiest to apply is the stick from SRD, especially for leather, apply in 3 inch X’s. A one-time application will last years and a stick is a life time supply.

If you search Kremer Pigments in the advanced search you will find several old post with the product numbers for Kremer Pigments.