I read about one years ago. it was a neck chain with a .22 bore brush attached.
You simply push the bore brush down the barrel of your small .22 revolver and let it hang there. If needed, grab it and pull. It will free itself from the bore brush and you are in business!
Then I realized, this thing would be pointed up right under my chin!
I’ve heard of the bore brush trick, too - and dismissed it for the same reason. However, a variation of that using a new 12-gauge bore brush and a bit of ingenuity will allow you to hang a shotgun from your closet rod. Tucked inside an old coat, only you will know it’s there. IIRC, Scattergun Technologies used to sell a similar gadget.