Check stall warning unobstructed. No need to kiss it.
That's a part of it, and I agree that some Cessna POH's do say to "check for blockage". Although, the reed in the horn itself is also vulnerable to bug interference (I just cleaned out the one in my 150), and the hose connection to that horn has been known to work itself loose, again, resulting in no audible warning, when there should be one.
If I were responsible for a pneumatic stall warning Cessna, which was being flown by multiple pilots, I would: Have the "kiss" test done as a maintenance activity before the first flight of the day, and recorded for the day. The person performing this test, a maintenance person, or instructor, could clean the area to their personal satisfaction. Thereafter, for later flights in the day, I would encourage instructors to slow the plane to the point of stall warning at a suitable point in the flight if possible, to confirm the function of the system, and record that it was functioning, when this was confirmed.
A bellows type of device could be made to work, though could be a fussy nuisance, so maybe easier to do the "kiss" way which is familiar to everyone - just one person, once a day only....