Well... if you're starting this breed from a foundation of 3 birds, I suppose you'll have to follow the example of other people who have started new breeds. First put great effort into finding more specimines like yours to add to your breeding pool. (Posting on BYC was a perfect start.) then you would want to look in the same areas these guys came from-- posters in feed stores, classified adds in ag rags, regional newspapers, etc. and then you need to decide on pure blood from OTHER breeds that will crossbreed into parents of your desired offsping. Cull for "type" traits, then breed your pool of mixed breed birds for enough generations that it becomes it's own true strain. If you truly have to establish your own breed, it may take decades, but I envy you that experience.
If you want them to be truly a breed apart from orpingtons, They need to offer something unique that an average orpington does not. Remember, Khaki campbells started out as nothing more than runner/rouen hybrids. If the eventual origin of the breed is as simple as "I found some unusually large buff orpingtons that produced superior table birds with beautiful buff coloring" then so be it.
~study the genetics of how buff coloring breeds. Also study genetics of "markings" like white rings, bibs, splashes, and the "dusky" gene so you know how to breed for the coloring you want.
~study the other buff breeds. As a duck fancier choosing hatchlings to order, it's really important that the customer know how your "bessemers" are different from other buff breeds the customer might consider (especially saxonies.) For your breed to appeal and catch on, it HAS to fill a niche nothing else does. Perhaps the meat has a different flavor (gamey vs. mild) Perhaps the drakes have different markings, or the birds have "lacy" feathering, perhaps they are better at foraging, good layers of gigantic eggs, what ever it is that sets them apart, you need to breed for that trait to create something unique. You need to sell more than just a name.