How does one safely barter such items as alcohol & ammo in a dangerous environment without setting themselves up for a robbery later? You'll have to leave your stash sometime.
I guess once the shtf for a few weeks and gobment hasn't arrived in your area a farmers market of sorts could start popping up. Being deployed in isolated conditions I've just seen how fast humans, even professional service members, can go bad.
Don't try bartering alone! I intend to be covered by competent riflemen. I will be armed to the teeth also. DO NOT be followed or trailed to your site!