A Mod could be a good all around choke for sporting clays, but I change chokes quite often...depends on the station and the scenario though. Honestly, if you want to become a better shot, I say hit up the Skeet field. I think it can make you a little more disciplined by it's repetitiveness...hence you should be able to pick up on your bad habits, be it not following through, not keeping your head on the stock, etc. Make it even more like a hunting situation and shoot it low gun (that's what I did when I first started shooting skeet) and I still do it today. Albeit, sporting clays is fun but I think if you are trying to hone your shooting skills, skeet would be a much better way to go about it.

As far as your hunt is concerned. You say you're going on a guided hunt? Are you hunting with dogs? Are these wild birds or pen-raised/planted birds? The type of birds you hunt will probably dictate which type of choke you use.