The trick to installing avrdude on a Mac is to use Homebrew. It will install all of the dependencies for you.
Once avrdude is installed, go to the Arduino IDE. Change the settings to verbose output. Compile and upload a known firmware update that works. Copy the output to a text editor and look for where the Arduino calls avrdude. Copy that line of code. Modify it in the text editor to point to where the holey-51.28.hex file is located and then run the line of code in the terminal.