Guidance Note on due diligence for private sector procurement

I am an experienced freelancer working in the field of international procurement for a decade - I have task assigned by an MDB to prepare a guidance note on how to conduct due diligence for procurement by private entities in MDB environment. I do have the knowledge as I have been working for this organization for three years so I know well my client but I struggle in structuring the work and writing it up. I can provide as a reference a document that partially addresses the same objective of my paper. the writer will need familiarize with MDBs Procurement Policy for financing private sector operations including PPPs ( ADB, worldbank , EBRD )