#1 - Shared interests and explorations
If you spend time watching dogs meet and hang out together, you'll see that shared exploration is an important part of their social behavior. It's a way to make friends, a way to bond, and a way to find and learn about resources (that's the wild part of them). I do this with Vida myself. I show an interest in her finds, she then reciprocates and shows an interest in mine. So when I pick a leaf of a plant and show interest in it, she'll usually try it when I offer it to her. I took her on an herb walk in Tecolote Canyon and offered her everything we tasted. The young wild mustard greens were her favorite, and she just started eating them like a goat (rip, chew, repeat).
I tell her about what I'm offering, that it's good for her, encouraging her when she eats it. Whether you believe dogs can understand our language or not isn't the point, the point is that they understand our intention. And the easiest way for us to clarify our intention is to talk about it (we're chatty, we humans!).
Nothing ruins it more quickly than a negative attitude. If you're filled with skepticism every time you feed plants you'll influence their opinion. Tell them why you're giving it to them with a positive attitude.
In food, treats, whatever. Nut butters can be a one way to hide powdered herbs (I use nut butter for some of my own herbs, as well as smoothies). Tripe can hide the taste of a lot of things. Most importantly, feed delectable meals! If you cook you can include herbs in the recipe. Tea can be made with meat broth.
If you think you can stick to dry food and add herbs to it, you'll probably fail. Raw food, home cooked, dehydrated, canned, or a combination of these is the way to go (the fresher the better). You may need to work extra hard at hiding new supplements, but usually they get used to the taste and you can ease up on the mixing.