That electric Tjanting is certainly a lot cheaper than some you will see advertised but I am inclined to think that, heated or not, they would prove more trouble than they are worth.
If you were filling them from a wax pot you would have to be so careful to prevent drips from the bowl while over the reeds and I am convinced that controlling the flow would be difficult.
The "finger over the hole" might well work but you would forever be dewaxing yourself before you could touch the next plate?
I have seen something advertised, specifically for reedplate waxing, that fits onto a pistol soldering iron in place of the tip. Even though this would give you trigger control over the heat I still cannot see what you do with the part full pot of wax when you get to the end of the plate!
For what it is worth I think you are better off using a simple spoon or, for single plates "stick" wax and a fine thermostatic soldering iron.