Reality check from some one that has been to thousands, milions, possibly a trillion auctions. Well probably not but I've been to a lot.
You're concerned about paying the sellers premium, but ok paying to advertise, have staff an ffl and security.
Stepping over dollars to pick up dimes comes to mind.
You can't sell your guns for more than the auctioneer at an auction because the buyers don't care about the stories or the sentimental attachment. They're there for a deal or because you have an item they want to add to their collection. If it's a typical auction it will last hours even going quickly. Once the stories come out, it grinds to a halt and the busiest part of the building will be the exit door. A slow auction is painful and unless someone is really after a specific item, they're gone.
At least 75% of buyers at every gun auction I've been to were dealers. A dealer will wait to the end no matter how slow you go. Because competitors drop out and they are getting deals.
Personally I'd have the full inventory priced out on gunbroker so I could have a limit set for each gun. Once my profit limit was passed I was done and waiting for the next. I did pick up a couple oddballs just because they were odd. The people that just wanted to buy a gun were there with the expectation of getting something cheap, end of story.
Most states you can auction your stuff, you can't auction someone else's stuff.
You need/want an auctioneer.
Unless you have a LOT of guns to sell you're not going to get one to do a private auction. It's not worth their time. But it's easy enough to enter them into an existing gun auction. Just put a reserve on them so you either make the $$ you want or it comes back to you. Your reserve has to be reasonable though. Once too many go unsold at an auction even the dealers will leave. It's not worth their time just to stare at guns and heAR "reserve not met, moving to the next lot".