I don't know if this has been covered in the previous 78 pages of this thread, but:

Ammunition priority should look like this:

Do I have a Clean Shot proc + Ammunition?
Use Split Shot.

Do I have a Slug Shot proc + Ammunition?
Use Slug Shot.

Do I have no procs + Ammunition?
Use Split Shot.

Do I have a Clean Shot proc + No Ammunition?
Use Clean Shot.
Strictly speaking, this priority would indicate that if you had a Clean+Slug proc up with ammo remaining, you would spam Split (or maybe Slug?) until you ran out of ammo, then use Clean. There is no solution above where you have ammo and use Clean.

So there should be one entry at the front that says:

Do I have a Clean Shot proc + Slug Shot proc (regardless of ammo)?
Use Clean Shot.