Over many years i've found cannabis (smoked or eaten) to be the best 'mucolytic agent' & 'expectorant' by far.
For me, this means that getting cannabis inside me, quickly starts to lower the viscosity & dissolve mucus within me.....which of course means it then needs ejecting.....

..on bad days it can take me several pipes & several hours of coughing the shite up before it slows down then stops, but at least...from a few min's after i start smoking i feel a progresive improvment...
It takes me from a state whereby i can manage to do almost nothing at all (even slight movements can tire me out) to having an 'almost' normal ability to stand & walk as the extra oxygen starts to reach my leg muscles.
Also, while i'm in the bunged up state, everything about life is unpleasant (depression..&..)...
cannabis soon alters this for something much more tolerable, even laughter.
The important bit, 'Yep' eating it works as an Expectorant/Mucolytic, though not as fast as a pipe or bong...
..as nasty as it may be..don't be put off by the snot that starts to come up as you toke...once that's outa the way everythings new & shiny-ish.
lob-a-lot ~