actually i started out with manual I find it easier actually to do the calcs in my head to just change the power by moving the flash closer or further away or bumping power up or down. Once you understand how it all works together its pretty easy really and just shoot a bunch of test shots and move stuff around, shoot some more and look at how things change, you will be amazed how much you can learn with a awilling model and a few hours just moving the lighting around to create different effects
ETTL actually complicates thing more because all the flashes take each other into account.
Sometimes its easier to just switch it all back to manual and have total control over each flash
Significant moving of the flash impacts the quality of the light.
Few hours? I did a new lighting set in 15minutes this morning.
The whole point of eTTL is that they balance all the time - you only have to get them in the right place and they take care of the rest