Recently I was painting a short haired dog. I wouldn't say I struggled with the fur, but he was a black dog and I wanted to add more definition to the fur and the way the light would be hitting the fur. I asked one of my past instructors for some assistance and she suggested that I pick up a "Filbert Rake" brush.
I of course jumped right out to buy one. I'm amazed at the difference it makes when painting fur! It looks a lot like a flat rake brush but because of the curved head, each stroke creates multiple levels of lines. I'm using it now on another short haired dog portrait for a client and so far I'm very impressed with this little brush.
I'm sure that it would be good for painting grasses as well. I'm hoping to give that a try soon as well.
Why not pick one up and give it a try!