Whether using oil, paint, acrylic, or watercolor, the same question arises. I'd like to stay on topic, but I also feel obligated to briefly mention the different types of brushes.
A very coarse hog hairbrush is known as a bristle brush, and I find it useful when I want to show texture and brushstrokes; it's also my workhorse for laying in oil paintings. Synthetic brushes tend to be white or some orangey-brown color or combination, excellent for blending, like painting a wall in a house without any marks. Sable brushes excel at refining, finishing with a more delicate touch.
So let's go back to our title—a higher quality brush is often designed by professional artists for a specific need. Therefore, if an artist needs a brush to have a flex or bend that is specific. And that specific need is for a professional artist who could be one percent of the country. So what about the rest of the artists in the world, and there lies the problem. There is a direct correlation between artists who draw at a very high level and shade with a pencil at a very high level, who also use a brush at a very high level.
So yes, you need a high-quality brush and no, you do not need a high-quality brush. I believe the solution is for artists to slow down, learn to measure and shade at a high level in a classical way, refine your eye, develop your eye and your touch, and you will see so many subtle things that go on within a painting. Once your eye is refined, and you have the ability to see those minute changes, your eye will be open to seeing so much more that is happening and changing, and then a high-quality brush will make a difference.
My touch is 90% responsible for the mark making and blending that I make in a painting. The brush will not matter if I do not have a touch to execute my desired mark with that brush! Having a story tells you why you desire that mark in the first place we call that Art Mapping - another blog :) .
So the answer is learning how to shade with a wonderful touch is the key. until then they are correct when you hear other artists say the brush does not matter, maybe we should look at how well they shade and are all their marks the same.
You see that is the issue. The variations of mark making with a brush require a highly refined artistic eye, with that, all marks will look the same.
So the real question is the decision you make at the fork in the road (Alice in Wonderland) do you stay where you are looking for a brush to help you, do you turn back and try something else, go forward and blindly hope you choose the correct path or listen to a voice who has been teaching over 200 adult artists for thirty years :) It is my desire to help, I am saying the answer is BOTH. A high-quality brush is a massive help when you can control your hand and shade at a high level being able to shade without and marks left behind and not smearing the marks in the process.
One other thing I left out is understanding Figure-Ground relationships, Lost and Found, NoTAn, HalfTone, etc. understanding art terms and where, why, when, how you use them allow the brush to be a tool for you. Drawing is the key when drawing comes with knowledge, :)
I need to change the word "expensive brush"; how about a high-quality brush? Rosemary Brush Company out of England makes the world's finest brushes. She will find the top artists in the world and ask them to help her design brushes that help them succeed. So, with the world of social media, and we're all looking for these brushes and say, "I want to paint like that person," well, it would make sense to have the same tool that person is using.
Now, Rosemary does not sell to retail stores, so there is no price markup. She will sell her paintbrushes to you directly, and therefore, you are saving quite a bit on the brush, getting it at a price just above wholesale but less than retail. Because you don't pay for sales tax, but you do pay for shipping, just make sure you order enough, like three to five of your most common sizes and favorite brushes, that it cancels the sales tax versus shipping cost.
When I sit down to work on someone's in our art school's painting, I always grab my bag of Rosemary Brushes because I know I cannot make the mark that I need to make without having an excellent tool.
Learning to shade and blend your strokes without smearing with your finger, learning to measure and draw, will take your eye to another level and does not require talent. The greatest gift an artist can have been desire, but somewhere down the line, it is up to the artist to take their skill level and desire to another level, and at that point, a great brush is imperative.