I have long been an advocate of the bigger the brush you use the better. For most of my paintings, even the smaller ones, I use a #10 bright, which is about 3/4 of an inch wide. To quote John Cogan, “get the largest brush you can possibly use for the job, then use the next size higher”. (John is one of my favorite artists, and definitely my favorite acrylic artist.)
The last few weeks I have been working on a large commission, using primarily a #12 bright. Yesterday, I took a break and continued working on a series of Yosemite paintings. I used the same #12 bright, which is about an inch wide, and painted an entire 16×20 using only the one brush. (I did use a #12 round for just the sky in order to have softer edges.) Although it is painted in a fairly loose style, I had no problem painting to the level of detail wanted. Although I might touch it up a bit, below is the resulting painting.
Morning Light on Glacier Point * 20×16