You need to set these values in your code if you're operating outside of the controller:
::PaperTrail.controller_info = { revision_id: revision.id, revision_source_id: revision_source.id }
::PaperTrail.whodunnit = user.id
The model will then pick the extra values up just like it would normally from the controller.
I derived this info from looking at the PaperTrail::Controller
module. Particularly, look at the set_paper_trail_controller_info
and set_paper_trail_whodunnit
methods that get run as before filters.