When I am making a large batch of flood icing, I vibrate it. I use my compressor from my airbrush, but anything that vibrates will do. The vibration causes the bubbles to rise to the top.
You can also buy a dental vibrator on ebay. I would hot glue a lid to it and set your covered bowl on top. The lid prevents it from vibrating off.
Another option is to bang your bowl on the counter after mixing in your water. I've also found a hand mixer to work well for adding water, without air because it is not being folded in like it is with a spatula or spoon.
I have been doing this for almost two years now and very seldom have bubbles.
Hope this helps.