Hi James,
once you have the entity guid (like project guid or task guid), get the responsible (field PARTICIPANT_GUID) via table DPR_ENTITY_LINK (field RESPONSIBLE = X).
Then get the BUPA_GUID from table DPR_BUPA_LINK.
Using BUPA_GUID, you can then get mor details about the BP.
After certain hotpackage, there is a report dpr_get_tree, which you can retrieve all the relevant database tables of a PPM project. If it is missing, just implement the note 1848890.
Kind regards,
Zhenbo