I can feel the strands of my hair breaking whenever I try to get tangles out when it's dry, and I hardly ever use a brush at all anymore. At this point, I only brush my hair to straighten it (with a blow dryer and round brush) or when it is already straight. When I wear it curly, I don't even like to finger comb it because I start to feel hair breaking all over the place.
One thing that I have realized is that dry hair is frizzy hair, but so is well-brushed hair (if it's not straight). A lot of the products out there meant to combat frizz are basically just silicone, which makes your hair look smooth in the short term, but dries it out in the long term. Silicones coat the hair shaft and are almost impossible to remove (even with sulfate shampoo, which is itself very drying). The coated hair shaft can't absorb more moisture, so it ends up getting even more dry, and more frizzy. Brushing hair that isn't straight just separates the natural wave or curl, which makes your hair look bushy and frizzy. Not brushing wavy or curly hair once you get out of the shower helps the hair clump together, which is what allows it to avoid looking frizzy. My hair, when I wear it curly, still has a lot of little fly-aways and a bit of frizziness, because that's just what my hair does. But leaving the locks of hair alone and letting them clump together into ringlets means that the frizzies aren't the dominant feature of my hair. I'm pretty sure nobody really notices them but me at this point.
Not all shampoos and conditioners are created equal, but I've become very skeptical of a lot of the claims that some brands make about what their products can do. In part because I've seen a ton of "moisturizing" shampoos that have as their first ingredient some form of a sulfate, and in part because none of them ever seem to live up to their claims. For me, using shampoo as infrequently as I can get away with (about twice a week at the moment) and using generous amounts of conditioner is what keeps my hair healthy. I use conditioner first to detangle (by loading my hair up with conditioner, then rinsing it out while I comb out tangles with a wide toothed comb), then to actually condition while I do other shower stuff, and after rinsing that out to get my hair set up for its ultimate style, I add a teeny bit back in that I don't rinse out.
I also think that avoiding unnecessary heat styling is key. I blow dry my bangs straight every morning, and they have way more fly-aways and split ends than the rest of my hair. I'm willing to live with it on my bangs, because my hair grows quickly and they need to be trimmed regularly, but it would be horrible to have the rest of my hair in the same condition. I only straighten the rest of my hair maybe once a month, because it takes awhile and is boring, but I otherwise let it mostly air dry. Finding a style that you like that doesn't require regular heat styling really helps keep your hair in good shape.