Dense Pack Cellulose?

I have a new construction Building I plan on using dense pack cellulose in the attic, floor, and walls.

Does anyone know how you can tell when it is dense packed enough?

I am working with housewrap with 1x4" every 2 feet vertically and metal siding on one side with planned poly vapor barrier on the other.
I am sure the first time I looked this up everything I read was "blow into poly" but now everything I see is "blow into netting".

I am pretty sure I will just have to go slow and hand dense pack it. But like for example, does the ceiling below the attic have to be finished? OR is vapor barrier enough to hold it up?

I've seen video where they were dense-packing using the cellulose sprayer/hose, and they just had a poly sheet stapled to the rafter bottoms. Then they would pack it in and you could see the poly was a little stretched, and then they put up the drywall. It seems that would prevent using those air-flow ducts so exterior air can flow through, the dense pack would collapse those channels right? If water dams aren't a concern maybe that's not an issue.