In any population without a wide gene pool, inbreeding is necessary. For best results, you should spend several generations culling heavily on health and hardiness first. Pick the fluffy polish-style top knot over the correct top knot if the ugly one is healthier! No breed with a small gene pool will be able to recover and become healthy again if you are breeding with the wrong priorities, and aesthetics rank rather low when the health of an entire breed is at stake, IMO. Outcrossing, even if totally unrelated, would get you nowhere if the outcross birds carry the same faults.