What kind of grass is it? It's not foxtail grass I hope! That can be very dangerous for dogs. That only came to mind because I can't imagine a grass that would stick like that. Is it like stickery? I guess you will probably have to try hand picking it off of him. I just don't know what to say. If it happens to be foxtail grass, you can read about that here:
http://www.almostheaven-golden-retri...g-dangers.html
Good luck...I hope others have ideas to help you!