Here's a picture made on one of the 'nearly' finished sections of my layout. The locomotive visible is a Proto2000 GP9, which I super detailed and painted in the Kodachrome colours recently. I still want to do a bit more weathering to it, but I'm taking my time.
Realizing that you're probably trying to show the loco, let me diverge by saying that what jumped out at me was how well the grass in the scene is modeled. Looks very realistic.
No one, I used a stiff hair from a paint brush. This is thin enough to look realistic, flexible enough not to break, and soft enough not to hurt you if you pick it up in the wrong manner. It was glued to an antenna base detail part. I believe it was a callscale base, but any manufacturer will do.
Thank you. It is a blend of a few shades of Heki static grass. I tend to use the more yellow varieties as opossed to the bright green ones. Bright green doesn't always work that well, it's often 'too green', but also depends what part of the country and time of year you model. I was aiming to give this a western / californian feel.