Just polish the areas on the trigger bar and connector with a felt bob on your Dremel and some Flitz. After that, hit the area with a bit of Hornady One-Shot and call it done. Grease will work fine initially but will collect crud eventually. One-Shot will not and it is very slick.
The Apex striker block is a standard part of my M&P 2.0 action job. That and a Performance Center sear housing available on e-Bay from Freestone Armory and your M&P will have a slick and crisp break and audible/tactile reset. Installing those two parts will turn any M&P 2.0 into a Performance...