Johno's Easy Vap -- The Next Best Thing?

Hi everyone! I hope everyone’s hives have overwintered well.
I’ve been looking into the oxalic acid vaporizer called “Johno’s Easy Vap”, after seeing it in several YouTube videos last year. I’m hearing a lot of good things about it.
Unfortunately, the guy who makes them is backed up on orders because there are so many coming in. Has anyone on this forum bought this device, and do you have any tips on using it?