I don't think you'd get sex linked chickens from the Buff Orpington x Barnevelder cross. Unless you have the Silver Barnevelders.
To get a sex link you need a red rooster (Rhode Island Red or New Hampshire) over (for red sex link) a silver hen (any that have silver in their breed name usually works), or over (for black sex link) barred or cuckoo hens. I do think that the Buff Orpington rooster would work as the red rooster, though the baby chicks they say are a little harder to tell at hatching than if you use a red rooster.
There is a thread at the top of Breeds, Genetics, & Showing section here on the sex link chickens and they name some good crosses that you could do. I'm thinking of trying them myself if I can ever create enough room to do it.