I have release triggers on both my Trap gun, and my Sporting gun,,,,Both K-80s.   Allem in PA. did both.   He guarantees his release triggers for life and is the recognized expert in this area.   He now has two versions.  The original was priced at $295 per barrel.  He has a new version that uses roller bearings, and by changing he bearing size, you can change the pull weight to set the trigger.   This one was priced at $450 for the first barrel, and $395 for the second.  I have one version on one K-80, and the other version of the other.  I slightly prefer the new version especially for sporting clays or doubles, it has a little smoother feel.   If you have a flinch, go with a double release right from the start.  Don't even think about starting with a release/pull
You can also send your gun to Krieghoff in Ottsville, PA.  According to their 2008 price sheet, they are $595 for a single release, and $995 for a double release.
And absolutely, it fixed my flinch, and made shooting a whole lot more enjoyable.   I still have some misses, by I don't feel like throwing the gun afterwards.   Nothing more frustrating than a flinch.