What I did on a Type 38 Arisaka (same exact design trigger/sear/striker) is start with fine valve lapping compound dabbed on the striker. Close the bolt and work the trigger just on the first stage. Squeeze & release over and over cleaning every once in a while and applying fresh compound. Do not let the striker fall as it will spatter lapping compound inside the reciever. Finished up with some superfine diamond compound I got at work from the die room. Polished the rest of the mating surfaces (trigger humps, bottom of sear) with 600 wet or dry paper.
I think it would be nearly impossible to free hand grind with a Dremmel and keep the sear/striker surfaces in proper alignment.
Delta co. 1st Bn 8th Inf. 1969.
Plei Trap Valley Duck and Dodge Club.