That Rub n' Buff stuff doesn't look like it drys or hardens, or more of a wax or buffing compound. Does it rub off if you touch it or leave any residue? A lot of reviews state to use a water-based clear coat if you use it on anything you'll be touching.
I'm also interested in how you etched all that detail into your growler, and don't say xacto knife
I would venture a guess that a reasonably coarse (110) Silk Screen would work - burn your image and wash out the emulsion, then tape firmly to the growler and etch ???
a bit of an investment, but you could use it many times...