My boy has flatter feet, and for a while it was hard to keep them short. But at first I didn't grind and didn't do it often enough either. A little bit of religious effort later kept them looking nice for shows and he built up his feet a little bit. Then when he matured he started maintaining so easy. I rarely grind him now. They don't grow nearly as fast and while they're much thicker nails than the girls, they stay short a lot easier and his feet look better. It's funny, the girls' nails used to stay so short and be easy to maintain, and now it's the opposite. But they have nice feet to start with at least.
As far as technique, I grind mostly from the tip and then angled back on the top half of the nail towards the foot. That will help get the quick back a lot faster than going at the same angle as the tip of the nail. Once I grind all the "tops" down, then I go back and do the underside of the nail where it can be kinda jagged like you said and give it a quick smoothing out. There is a picture somewhere showing the proper angle to trim at, but I have no idea where. lol I think it was posted in a Basenji mag a few years ago, but I believe it's online too? Well I looked around and can't find what I want, but this gives an idea:
I use a little more vertical angle than the line they draw on the nail.