Positive displacement pump rust removal

[PFBlowerinstall]

I have a question regarding PD blower. Maybe someone can advise. I have a roots PD blower (616 dvj) I purchased new. The unit sat for a good year or so - covered with a tarp and now im needing to clean it up (Without taking it apart) any experience with this process. quickest methods that won’t harm the lobes

 

[Compositepro]

I would turn the rotors by hand to oil and make sure everything was free to rotate. Then spray oil into the inlet while running so that the oil suspends the rust dust and and carries it out the exhaust