The 'lost items' procedure is the only way to use the holy water inventory files.
The duplication method is similar, but assumes you are using inventory files from two successive saves made in the same game. Keeping inventory files from a different save will cause problems, so the 'lost items' procedure describes how to backup and restore your original files, just using the downloaded ones long enough to get the required item(s).
AFAIK nobody has figured out how to add specified items to the inventory files by hex editing. If you don't mind hex editing, though, you would get the same effect of making permanent potions by giving yourself extra stat points.
