For embedded fonts:
Many ePubs with embedded fonts do not include them in the manifest. I don't know what the standard says, but it is presumably safe to skip step 4.
Steps 3,4,5 assume the fonts go in the same folder as the content.opf and stylesheet.css. I have more often seen the fonts in their own sub-folder of this folder. If this is called "Fonts" then use (step 5):
For on-device user fonts:
This also works on Sonys (ePub custom Fonts on 700, 505, 300, 600
) and Hanlins ( Fonts and Epub - What works on Sony, Works for Pocket Pro too!
). All that differs between the Cybooks, Sonys and Hanlins is the location of the user provided font directory (e.g. SD card vs internal memory) and how it is named in the src: line.