Yes, because my first horse Prince wouldn't let anyone touch him practically but he's come a LONG way just by me communicating with him and riding him often. So ya, I would definitely say grooming helps!!!
The way to a baby colt's heart is through butt scratches.... or any itchy spot they cannot reach well with their short little necks. My babies went from "Don't touch me, monster!" to "Hey, you are here to scratch ME aren't you?" Selfish little devils. This year at one point I was trapped in a triangle of itchy babies, each one scratching the next ones hips. It was cute.
ABSOLUTELY :) I had to move to find a job, but when I'd come home, all I had to do was go through the motions that we used to do on a daily basis and she automatically relaxed. I gave her massages too, that always gained a bit of trust and relaxed her whole body(A fart or two was like saying welcome home...lol). The closer you get to them, the more trust you gain.. like clipping anything on/around the face.