Yup - if I had a buck for every "rapid-fire" trigger shifter I saved by doing as described above, I'd be rich. I've actually acquired several nice old mtb bikes for peanuts because the owner didn't want to go through the expense of replacing "broken" shifters.

I've yet to come across a malfunctioning set of trigger shifters that weren't rendered fully functional by de-gunking the pawls. And photostudent is right-on.... you have to expose them and work them while you spray. The original grease just hardens up over time, and needs to be cleared out.

Also, if your brifter will shift up to the large cog but not down to the small cog (pull cable but not release it) it is almost certain that the problem is a gunked up pawl.