Hi Anthony
Nope I can't access MWB through the housing that I used on the Mahoney. I've got an Ike housing and Sony PC350. The PC350 is a top end consumer cam (discontinued), but I wouldn't consider it to be prosumer or pro. It will MWB through the touch screen, but much like Ike said in his reply to you it's difficult to access through a housing. (I've tried it with the PC1000 and HC1 models and found it very awkward).
I use a UR Pro blue or green water filter and I've experimented with and without lights. I would say that lights are a lot more difficult to get good results from when you don't have MWB, so unless I'm in murky water or at night I rarely use them.
The main part (for me) is colour correcting while editing. It takes a bit of practise to get it right (or if not right then as good as you can get it) and it will never be a replacement for MWB while diving, but the results can turn out ok. Most entry level NLE editing software will allow you to do this, but the best value for money in my mind is Premier Elements. You can get better results from Premier Pro or Apples Final Cut, but these are a lot more expensive.
I'm glad you enjoyed the film! Honestly the Mahoney was one of the best dives I've ever done, I'm just a little sad that no matter how much I enjoy the footage I shot, I still don't think I did it justice. It should have been a 40 min dive and I was still down there after 70 mins when they sent someone back down from the boat to get me! 
Cheers, Simon