The bucket is supposed to give more accuracy if you change the length of your tube and also make getting your accurate starting point a lot easier without removing/adding a couple of drops of water to get to the right height in the tube.

The way I do it is:

Set up one permanent post to which you mount your bucket with the water level at the same height as what your top of the wall will be - this is your reference/starting point and will be the the exact height of the top of the wall, so make sure it's correct. Tape/fasten the far end of the open ended tube to a second post at least 6" taller than your wall - you can give this post a 1.5x1.5 foot plywood board base or a tripod style base so it's self standing to make life easy on yourself. If you have a tall enough camera tripod, it will work too, but get dirty in the process.
This saves you from pounding it that post you were complaining about over and over...
Set it immediately beside the bucket post and mark off the bucket level on teh tube or the post (water in tube should also be at this mark).
This mark is what your level point will be, as you move your tripod post around the site, the water in the tube will be either:
at the mark - meaning you're exactly at grade
Below the mark - meaning grade is too high by the difference
Above the mark - meaning grade is too low by the difference and you'll need to backfill some dirt.

Hope this makes your water levelling a littel easier.