Can I use your Leather Filler before applying the dye to fill some cracks?

No. You can’t use leather filler or our Leather Repair Resin and leather dye together. The Leather Dye is alcohol based so it will soften the filler or resin. If you have an aniline leather, then no filler just dye. If you have a finished / pigmented leather then you can use the resin or filler and leather colour, which is leather paint.