Thanks for help and feedback! Speaking about how we did the leaf painting: at first we wanted to do it just by painting the sprite, but we couldn't. But we are good at 3d and shaders, so Vertex Color came to our rescue. While painting, we did a Raycast from camera to cursor. If it hits the foliage mesh, it changes the color of the nearest unpainted vertex from black to white, which we used for blending. The rest happened in the shader.