that would depend on the best typed bird you have available to you, and how long of a project you want it to be, to get the color back once you have type.
The man I know who did a good job of it used a Quality Mottled. A good Barred would be another good option. Below are 2 males of his breeding. I bought him out about probably 3+ years ago. Not an easy project but very rewarding. Do not attempt unless willing to cull at least 90% each year. If you want the mans name PM me for more information.