Firstly create another 3D Container bigger than the cloud container but with a resolution of 20,3,20. We can get away with a lower resolution here due to the fact the haze isan't complex. Set up the Contents Method the same way as the cloud layer.
Open the Shading tab and set the transparency to a value of 0.867 for RGB, adjust the Edge dropoff to about 0.34. Make sure the colour is completely black as we will use Incandesence to light the haze as opposed to colour for a more realistic feel. The colours should be as follows.
Selected Position=0.000, Selected Colour=R(0.494) G(0.773) B(3.000)
Selected Position=1.000, Selected Colour=R(0.871) G(0.905) B(1.000)
Set the Input Bias to -0.2 and make sure Incandesence Input is set to Y Gradient
This value should be a standard value across the board of about 0.820 but this really depends on what you what your scene to be. Anyways thats the gist of it, not very hard to create a simple Haze with fluids. Enjoy!