Hi EweSheep,
It can go very fast if the space is their to do it, once you get the lavender into the breed your after its just a matter of choosing the birds to meet the standard for them or as close as possible.. Of course if you have a lot of unwanted traits to start with, those can be problematic to your project and you will end up with lots and lots of culls, if that is the case than you select what your after and carry on...
Our one line is so close to orps now, the bloodline had straight comb to start with and the brown egg gene is coming along with it., not to much to work on other than selecting size and conformation from our breeding in the offspring, we may even re-breed again with another line of black orps again down the road sometime, we must wait and see what the lavender looks like and address the issues as they arrive.... However i do also have two other lines as well, one with straight comb, but has other traits not desired and most of the chicks from this line will be culled out completely, then third line has pea comb carrying the blue egg gene and being used on the araucana project. which is going great as well as the lavender orps project.
Time and Patience is needed lots of it, as it is with any breed/color. i have to recommend everybody try a project of there own, just crossing two breeds and see what the out come is.. it is a lot fun..
Charlie