I've always thought that the best way to sucessful AND consistant flash is to take complete control away from the software and run the show yourself.
People tend to think that using flash is complicated and that we need the camera and the head to work out all the questions and the answers for us. It's really pretty simple when you take a step back and look at it again.
The only difference between flash and existing light work is that we can't measure the light from the flash and then set the camera. Well you can if you have time to wave a meter around but most people dont. We can control the output though so setting up our exposure is not all that different.
Give it a go. Set the camera (on a tripod if you have one) with the flash on so you have a fixed distance to an object. Have the shutter set to the flash sync speed and the flash to full power.
Now adjust the aperture untill you have an exposure you're happy with. You've now got a base to work from....;
a full power flash burst to a subject at x distance, with x ISO needs an f stop of x.
If your subject is nearer, you need less light, further away and you need more. Without going to far into the theory, light works on the inverse square law, which means if the subject distance doubles you need four times as much light to maintain the same level of illumination. All that means in english is that you need to expriment with distance a little and you'll very soon be quite instinctive. If the subject moves from 5ft to 10ft away, you need to open the aperture by two stops.
Once you've got a base figure to work from, you have three ways to control the flash. The flash output power, the ISO and the aperture. Since all you need to do is raise or lower the one of these depending on distance, you can chose the one that most fits with your needs at the time. For instance if you need DoF control, then flash power or ISO are the better options etc etc.
This is really all very easy to get to grips with and once you start to use it becomes natural very quickly.
The other thing that comes into the equation when you are using fill in flash is the shutter speed. When you are using 100% flash illumination the flash duration is far faster than your fastest shutter speed but when you have ambient light too, the shutter allows you to control this without any effect on the flash.
Anyway, enough waffle from me.
