Hi David
Its hard to advise you without a few more specific details i.e. The time of day/night you are trying to recreate? What's going on in the rooms - props, action etc? Static or moving camera? What kind of motivated light sources are there? The fact you are using 500T fo the INT suggests it could be a Night scene. Based on that assumption you could consider lighting from the underneath the eyeline. I recently shot a clip in a small apartment with light coloured walls with a brief to achieve a noirish look. I utilized alot of 'up' light hiding fluoro tubes, small kinos, bounces round the place and picked out the edges with dedo's concealed in corners or cunningly framed out of shot. Keep a few large flags around for anti fill its amazing how the light bounces around in those small rooms especially if the walls are white. Another thing that might suit you is a boomed top light. I often use a flathead/image 80 or 4x4 kino boomed in from near the camera to create a movable top light. For the flathead you will need a heavy duty wind up stand (preferably with wheels) and something like a Matthews Junior style boom arm. The 4x4 kino can often be rigged off a baby syle boom provided you don't need too much extension. Its great because with a little adjustment you can make it a back light, a frontal key or even a toppy fill light.
Good luck with the EXT scene it sounds like the sun will be your best help with the God Rays. If you do over expose a little as suggested by "thinkmonkeymedia" bear in mind God Rays will lose intensity with overexposure. If you end up using a mirror or a light to achieve this effect playing it back towards the lens will increase the intensity. I'm not sure what kind of fog machine you have but controlling that effect can be a nightmare. If you have the man power (and a cerified saftey officer) you could try using multiple pots of frankincense upwind to create a haze. Be careful of the fire risk though! With HD i try to avoid overexposure as it generally clips out the highlights more readily than the blacks.
Good Luck
