Maybe I’m kind of old fashioned, but I go in person to one of a few local consignment tack shops. Of course, I know I’m lucky to live in a place where this is possible and that not every area has them.
Rather than just using Facebook Marketplace, find some of the bigger used tack groups and list your items in there as well. When selling, I got good results by looking through the groups each evening for people who posted “in search of” types of items that I had and then responding to them directly.