Make 3d grass in your 3d editing software of choice - poly model it like you’re modeling anything else. Turbosmooth it.
Vertex paint some color variation if you know how to do that.
Duplicate the grass until you have a good amount - you can use the object paint feature if you’re using 3DSMax, but don’t go crazy you still want it to have breathing space.
Bake it onto a plane - normal and diffuse you can get the alpha from the diffuse.
Make a couple versions of this.
And you’re done.