Before I add the 3gal of water to my 2.5gal wort, I shake the water in a plastic 1gal water jug. I shake it up for about 5min. A whole lot easier then shaking 5gal of wort.
I have an O2 stone, but I only use it in starters and meads. I just pour my wort through a strainer into the bucket. It gets a nice foam to it and the yeasties don't seem to mind.