This. It takes practice, and its not something easily explained or shown for that matter but is way faster and you can cut a perfectly straight line with any sized brush once you learn it. Back when I was painting for a living the biggest thing I had to get across the new hires is to only dip the tip of the brush maybe 1/2" in the paint, slap it on the side of the Can a couple times, no scraping on the rim, then knock the initial excess off by doing a couple strokes on the wall before you start trying to draw a line. Ohh and hold the brush like a pencil you're drawing a line not clubbing baby seals.
And for a quality brush try Purdy. I like the blue bristle ones in a 3" not sure the actually name/model but any paint store other than Home Depot type places will know what a "blue bristle" is. Expect to pay $30 or so for a descent brush.