The unbrick discs conform to the Wii DVD size requirement of 4.37GB and like Wii discs contain a load of rubbish data with a tiny amount of useful data.
The .rar download for the Universal Unbrick Disc v2 is only 5.2MB while when extracted it will fill a single sided DVD.
You just burn the iso using Imgburn at 2x or 4x, as you would any other Wii backup. DVD-RW provide better compatibility but +RW probably works for the one off.
As it's a banner brick with luck you should be able to load the recovery menu using savemiifrii and provided you have a modchip or cioscorp installed you'll be able to autoboot the disc.
Use a gamecube controller plugged into port 4 and press Up, Down, left and right on the D pad at the same time.
There are a few threads dealing with Banner brick recoveries, it will certainly be worth your time looking through them in some detail.