NWPlayer123 has posted a detailed article on GBATemp, discussing various aspects of the Wii U’s Firmware, here are the tools she suggests one uses:
- OpenSSL is needed to decrypt the various binaries once you get them from NUS.
- A hex editor, I use HxD even tho there are probably better ones.
- Windows or Linux recommended.
- The Interactive Disassembler, or “IDA” Pro, I am currently using 6.8 and I’ve also used 6.1 and 6.6 in the past, 6.1 is too outdated to have support for Paired Singles, the unique instructions that the Gamecube, Wii, and Wii U all use.
- Something to keep track of all your data EG Dropbox or MEGA so it doesn’t get lost as easily.
You can read the full article here