I'm not sure on the popular bulls now , but Joe Butt of Valley B Enterprises in Cleveland,Tn might be a good resource. He fits quite a few Brahmans for folks in the Southeast and helps with some of the sales. One thing I see in the Brahman breed I don't see as much in other breeds is having semen on some of the top bulls for sale foreign only.
I think dash's bull is from here. I'm going to AI a few to a bull from here. I haven't made my final selection yet. http://v8ranch.com/herd/brahman-sires/
V8 and J.D. Hudgins will be the two most prominent Gray breeders you'll find Bulls from. I don't have any experience with them, but they have been in the business a long time, and have built a reputation for quality stock.The Texas folks on here will have a lot more insight than I will though.
I know Elmo is a good bull to use of course he's off of Hudgins ranch. Must all your grey's are going to come off of the ranches mentioned earlier. I guess it's a matter of searching of searching out what you want in a bull. Partin and Partin have really nice bulls but again its hard to not use JDHudgins bloodline. Now don't get me wrong Hudgins is the best of the best to use.