You can find a local dealer who will sell on consignment. They charge a percentage fee of the sale price. Or you can sell directly to the dealer, though you will take a huge hit since they are going to have to make profit on reselling it. Direct sale to a known local dealer is the quickest and easiest, though you will get the least amount of money for your sale.
You can try to do an in-person sale to another person. Check if there is any kind of local gun-owners web site in your state or region that has a for-sale forum where you can post the items. There is such a forum in my state, that I have been a member of for many years. I would probably have to pay for a subscription to list a firearm for sale, but after that it is just the normal stuff of agreeing on the sale with the buyer, meeting them, and transferring the firearm.
Check local/state laws regarding transfer. Some may require you to go through an FFL who will do paperwork (and charge a fee), others may just allow face-to-face transfer. Personally I would want to have a bill of sale identifying both parties by name and identifying information such as DL number, the firearm including serial number, date, and price paid. That gives both me and the purchaser a paper trail in case anything came up. Though some face-to-face buyers don't want to do that because of "reasons".
Gun shows are another place, where you can haggle with a dealer or see if there are any other participants willing to sell or trade. Expect some hard bargaining, since they are all trying to get the best end of the deal.
You would need to be smart and safe about doing the transfer. Choose a safe location, don't go alone, abort and leave if something looks off. Also expect that whatever price you agreed on, to have them show up with a bit less cash and tell you they had some unexpected expense and this is all they can afford, in an attempt to last-minute low-ball you. I have even had that happen with friends. And if you ARE selling to a friend, don't fall for the "Hey, I can pay you $400 now and I will pay you the other $100 in a month." Tell them sure, no problem we can wait a month, let's do this when you have the full $500 we agreed to.
I happen to live in a state where it is quite easy for there to be a 6-8 hour drive between me and a potential buyer or seller. You might have to agree to a midway point to meet, which is where being careful about location comes into play. If I were doing a sale locally, I would probably suggest a meeting at a local firing range for the transfer, so the buyer could look at the gun and even verify functioning without there being any issues of pulling guns out of their containers in a public area.
Check out this site, which has breakdowns of laws per-state and good recommendations about private selling. They (as you can guess by the name) also will be happy to buy your guns. But they do have good advice and links to many other sites for help in determining the value of your firearm so you can set a reasonable price. I have not used them but they seem like a good place for information, at least.
https://www.cashforarms.com/blog/how-to-sell-a-gun
