What about just focusing through the view finder in the field not using a tripod or live view.
in the field it is not a problem-being critical ( wide open) not every shot is perfect but even in indoor situations about 80% is well focussed. and If you turn a zeiss to infinity you are certain infinity is sharp.
and an zeis 21mm has a large depth of field so it will not be difficiult to produce sharp pictures.
I found it a relief to leave the autofocus and just look and turn the focus where your eyes leads you- and it is not that much slower if you get used to it again. - in some cases it is faster.
The autofocus of the D3 is very precise still liveview is the true perfect solution for a perfect sharp image.
the dot in the viewfinder that tells you the picture is sharp is not precise enough for some lenses. the 1,4 zeiss at 1,4 is very sharp wide open- but I can turn the focus on six positions within the dot mark area and only one of them is really sharp. With the 2,8 21mm lens this problem is an non issue.