I have a black leather coat which is showing wear. What can I use to c

Would leather shoe polish work. Somewhat like an old fashion shoe shine. Small amount rubbed on worn area with rag, soft brush to penetrate polish/stain into area, and last polish with a different clean rag . Or ask your local shoe repair shop for any suggestions.(i've done this on edges of jacket and coat openings when they start to show wear) Ask repair shop for suggestions on a sealer. Make sure he is your go to for other repairs beyond your expertise.(just sayin)

Depending on how large of an area, you could use a black marker. I use a black mark on the scuffs, on my black boots or black shoes. I hope this helps???? 😇

You can buy leather dye. After you dye the worn places, go over the whole coat with a good leather conditioner. You can find lots of choices at a farm supply store. I would not use shoe polish.

https://www.walmart.com/ip/Leather-Refinish-Color-Restorer-Dye/160770718?wmlspartner=wlpa&selectedSellerId=2727&adid=22222222227054467822&wmlspartner=wmtlabs&wl0=&wl1=g&wl2=c&wl3=155024918632&wl4=aud-310687322322:pla-264571570526&wl5=9004541&wl6=&wl7=&wl8=&wl9=pla&wl10=113548438&wl11=online&wl12=160770718&wl13=&veh=sem

I suggest using the shoe polish paste wax in a can. Light it on fire with a match, and it will liquify, making it much easier to apply with a rag (after you have blown out the flame). Once it dries, buff it with a rag. The iiquified polish will fill the voids and irregular spots. If it needs to be shinier to match the rest of the coat, you can polish with 5-Day Deodorant pads (old military trick for polishing dress shoes).

How bout going the other way!. Sand it and turn it into nubuck. I do this with shoes. Completely different, more earthy look.