By no means do I want to start an argument, but the idea is to share our experiences/thoughts right? With that being said....
I personally would not put filler directly on bare steel. Filler is pourus(sp?) and can actually absorb moisture, which would be undetectable to the eye, causing rust later in the car's life. Personal experience we used an Etch primer on CLEAN, Oil free metal(even natural skin oil, like when you touch the metal with your bare hands) to eat into the metal. After that we used a good quality Epoxy primer. The above two layers were put on as 'wash coats'(ie. VERY thin coats). The car was left for a few days to 'cure', to make sure ALL sovents evaporated etc. After that we used filler. I have seen cars come back with paintjobs not older than 4 months were filler started to lift, and upon closer inspection, I found that no Etch primer
or Primer was used.
Then again, this was my personal experience/s...
