The HF and the External scripting functionality works in the same way. I have one sample that I can show a little of (but not the whole thing as it was delivered as part of a professional services installation.
Here's the external component configuration:
When this node executes we concatenate the path to the script file and the parameters and make a CLI call.
Here's the parameters in their entirety:
"$FFin$" "C:\Xerox\FreeFlow\Core\Data\Save Destinations\Pad Barcodes\File - $FFOrder ID$.pdf" "C:\Xerox\FreeFlow\Core\Data\Save Destinations\Pad Barcodes\File - $FFOrder ID$ - merged.pdf" "$FFout$"
$FFin$ is the job file.
$FFOrder ID$ is the Manifest Order ID (this is to ensure the referenced files have a unique name)
$FFout$ is the folder into which $FFin$ should be saved after it is modified.
This this is a batch file, the parameters are referenced as %1, %2 and %3 within the script.
The Batch file invokes a CLI app to manipulate the file and then moves the file to $FFout$ (referenced as %3 within the batch file).
