This might be a convoluted way to do this, since dockutil has an --allhomes option, but I like using docklib, and so this is one way to go about adding an app to the Dock via a custom package, leveraging docklib and Outset.

Here’s the example custom package: gimp_dock.

When you look inside, you’ll see it uses GIMP as an example, but you can easily adapt it to add any app to the Dock.