I believe the scan gauge will work.
Create an account on the Cummins Quickserve site, once you do this register your engine SN. You'll then have access to lots of information. https://quickserve.cummins.com/info/index.html
There is a tab at the top labeled Service, open it and then go the Electrical Diagrams link. It will provide a diagram showing both the engine and coach wiring for engine. If you have an ECM the scan gauge should work.
One thing that can cause excess blow by is if you overfill the oil. If I put in the recommended amount I use oil. If I leave it a couple quarts low it doesn't use any.
I've also put a catch bottle on the bottom of my engine vent tube, which comes down next to the oil filter. I do catch a little.