Be careful when selecting a gun smith to do action work on S&W j-frames. They aren't real easy to do... not at all like their bigger brothers and sisters.
I shoot quite a few j-frames. One, which is a M60 that gets carried from time to time, had an action job, trigger contoured and polished, and hammer radiused and half-bobbed for about $135. Methinks $100 is a bit steep for just an action job... unless your smithy is real good.
Since I shoot j-frames a bit, my blister hardened into a callous long ago. But my blister is like the one that VL described... not necessarily from serrations.
Another reason for keeping the serrated trigger is similar to the reason VL stated also. Once when I was wounded (stabbed) during an armed confrontation (back in 1972 or 1973 BC (before communications)) I had to hold two guys and a pregnant woman at gunpoint awaiting arrival of the police. I remember wiping one hand off on my clothing, taking the gun (a P38) in it while I wiped the other hand off... repeating several times. Man oh man, blood is slippery stuff!
Anyway the narrow triggers with serrations are sometimes referred to as combat triggers. During stress... or any other slippery situation... serrations, stippling, etc. are good things IMO.
Now, you could get another M60 (can't have too many SS j-frames I always say) with a smooth trigger for most of your practice. Or toughen up and get a callous. Or if the band aid is working use it... or a piece of mole skin. Even with the finger covered you should still get a callous real soon.
But, there is no reason not to take the edges off the trigger as VL also suggests. Just be mindful that j-frames are real finicky about getting work done on the insides. But, a pro gunsmith... as WeShoot suggests is the only way to have this done. The right job will make that m60 of yours hum! In that case the $100 is well spent.
The first guy to respond is writing from where I was born. Sadly, tho, my parents brought me to frozen Michigan when I was two and even sadder I'm STILL here.