The best tactic is to get a Golbat - which doesn't take too much effort as you can catch them pretty easily in Victory Road, get Mean Look on it, use that to stop it from escaping, then switch to a pokemon with sing or grasswhistle, then whittle it down to red and throw ultra balls to your heart's content.

Somewhat deflated. It gave me purpose, and like i said, i had long since forgotten what i had planned to actually do afterwards. I think it had something to do with making a better battle team (since my team is strategically hampered by the need for HM-users. My Golem and my Empoleon are loaded down with three HMs each)

Nicely done on your Mesprit catch. Cresselia is going to be a bitch for you. I recommend catching a Roselia (or evolve a Budew) and teaching it grasswhistle, or if you're very serious, breed one with a father that has the move Sleep Powder so the baby learns it at birth.

Actually, I use a Bibarel and taught him 4 Hm moves haha, most of the crap ones (cut, rock smash, rock slide and waterfall).  The rest of the HMs are better moves so its all good. 

That idea with the Golbat is good, I was just gonna try and give it a staus ailment. 

All legendary pokemon am cry before mighty dusk ball!

Is that your experience, because it seems that ball is most effective against Uxie when I try.  Interesting....