Yes we use the Orpingtons as they are geneticly the same since the Australorp was created by using them.
We have been breeding the splash to black with results of some buff in wing bows and hackles, so our next attempt is breeding back to black to see if the buff will cancel out.
We also are going to create some Blue Orps and breed them into the blacks to see if that will also be positive for black on blue only without any buff traits.
I have heard of folks using any blue breed to mix it up with the B.A.s but im not really for that since many have to deal with skin color and feathered legs which just take up more time triyng to remove and may return several generations later (not good if you are selling hatching eggs and want to keep a good name in the poultry world).
you replied, so what do you know?
Not much. Just curious.
I do however know that Australorps were created from Orps though.
I wish you luck in you endevour. I'm currently working on another project or two so really don't have space for anything else right now.
I'll be watching your progress so post pictures if you can.