Most "big time" newspapers won't take gun ads. Lucky if yours does.
I've sold in Atlanta back when a rag called "The Atlanta Advertiser" use to take gun ads. Wasn't a particular problem. We chatted on the phone. Got some bask id from the caller over the phone. What's your name, were do you live and work. Who do we know in common. Where do you usually shoot? Do you compete? Not direct questions but more 5-10 minutes of "get to know you" conversation. We'd meet in the parking lot of a local gun store/range so anyone seeing us handle guns wouldn't think twice about it. I always carried. Usually by the time I got to the face to face meeting we'd know who each other was.
Now these were in times before GunBroker, before widespread forums and email lists. So it was the basic way, other than posting ads at the local range on their bulletin board. Which, if your range allows, works good for shotguns.