I use Super Clean (I buy it by the gallon). I just soak parts in it, then scrub with a toothbrush.
Be Aware: As harmless as Super Clean appears to be, it is extremely caustic and should be handled with care.
On the rare occasion that hasn't worked, brake fluid hasn't failed me yet. (as effective as it is, I avoid using it as I really have no way to dispose of it properly).