Dry fire the **** out of it. I am doing that to mine and it has improved ALOT. I also cleaned it a few times and used Slip 2000 EWL and the grittiness is gone. Sit in front of the TV and dryfire it as much as you can.
For those who have never used a really good trigger--smooth, proper length of pull, and a sear break that is safe but not too heavy--any trigger that makes a gun go bang will do. I don't understand continuing to shoot a substandard trigger hoping it will slowly improve.
One of the best $50 accessories I ever bought was a Lyman digital trigger pull gauge. It has helped me fix many, many triggers and paid for itself many times over.
I understand dry firing is a fairly cheap, labor intensive way to eventually help smooth a poor trigger. It may reduce the pull weight a little, but usually not very much. It is certainly better than wasting hundreds of dollars worth of ammo to get an almost acceptable trigger pull.
I believe a trigger should be as you want it (
at least what the factory claims) right away and that you should practice with it that way, not in a decreasingly less sucky configuration. This is a tool, a machine. It can be adjusted and fixed to meet your needs.
Following You Tube videos for disassembly and polishing component parts is more satisfying and will yield much faster and better results than a bunch of dry or live firing hoping to improve a trigger. I polished my Shield trigger components and it smoothed out, but the pull weight was still above 7.5 lbs.
I broke down and ordered an Apex Shield Carry Kit (SCK) and installed it. Not really difficult. Now I have a smooth 5.5# pull weight and other distinct advantages over the shipped factory setup. Worth it, but it certainly makes your investment in the gun go up.
You will find your Shield trigger pull, if it is like mine was, is probably 8.5 lbs or more. That's ridiculous on a small gun. It makes it very hard to shoot well--either accurately or fast, both of which are desirable for personal defense. BTW 8.5 lbs is 2 lbs over the marketing claim of 6.5 lbs, or a whopping 30% heavier than what they claim. If this is a machine you intend to use to save lives, the critical trigger component should be the best it can possibly be. S&W sets their claim at 6.5# as an average, I understand, but it is an average that has a lawyer's margin of error (extra weight) for "safety".
Once the trigger job is done, you can (and should) dry fire
a lot, and practice with live ammo too. You will have better results and be more satisfied with your Shield with an improved trigger.