Please help me ruin a perfectly good canvas field coat

Just wear it. You haven't earned the character, yet.

When I need to make the fresh hem in my jeans match the rest of the pants, that's when I reach for my revolver Dremel with a sanding wheel.

Best way to distress without breaking the buttons? Presumably remove the buttons first? :^)

Wash the guts out of it a few times. Use fabric softener in the rinse cycle. Hang it to dry instead of putting it in the dryer so it will be slightly wrinkly. Use a nail brush or some other stiff brush and rub it over the coat. I guess you could take a pumice stone or some other device and use it to slightly rough up the hems and collar. Roll around in it on the ground. Hike through thick brush while wearing it. Beat it against river rocks. Let it bake in the sun and fade.

I would look at your old jacket, that you think is great, and figure out exactly *why* you like it, and set out to duplicate these qualities on your new coat. Everyone likes a different sort and level of distressed. Is your old jacket awesome because it is so comfortable and stretched out in the right places, or does it have a worn in texture and ground in areas of dirt that you love? Your body wears a garment in a different way from anybody else wearing that same thing, so duplicating the areas of wear on the new jacket, based off of your old one, would look more natural on you than anything randomized. You can also go to a fabric store and try to buy a yard or so of matching fabric to your coat exterior, to experiment on. I would try extremely diluted bleach applied with a toothbrush and a light hand to highlight some areas, and extremely diluted shoe polish in a rich brown shade for the dark bits. And then machine wash the hell out of it. If you have one handy in your kitchen, a microplane grater might do interesting things to your hems and whatnot. Depending on the material of the buttons, you can buy chemicals that will tarnish various metals at craft stores. Gotta say though, I would just *wear* the thing. A nice new coat is pretty snazzy, too.

You're not that far from a woods. Could you take it to Runyon Canyon Park and maybe go mountain biking or something like that in it, roll down a few hills in it, have your buddies throw you off the side of a path? Hiking up in Griffith Park? You might as well take it out and get some use out of it now-- it's still plenty cold in the mornings.

Technique from wet felting: roll it up in a piece of old pool cover, get it soaking wet and set a gang of kids on it in the driveway jumping up and down. Also, you could bounce a basketball with some sandpaper taped to it on top, also on a gravel or concrete driveway...

PoserFilter. That said, light sanding of scrunched-up fiolds (in the right places) of fabric should add some weathering. Seeing as how you're in Los Angeles, do you know anyone in the television or movie wardobe/costume business you could ask about how they age clothes?

You haven't earned the character, yet. PoserFilter No argument here. :^) I am, however, perfectly comfortable being a poser in this regard. Thanks everyone.