Here's one portrait for you that was lit by the “Chinatown Special,” my DIY Beauty Dish, and made with the Nikon D3 and Nikon 70-200mm f/2.8.
I made this image at f/4, ISO 200, and 1/100 at a focal length of 140mm.
When balancing flash with daylight, there are a few important factors to consider. Ambient light is going to be informed by the camera exposure of ISO, shutter speed, and f-stop. Flash exposure is going to be dictated by flash power, f-stop, ISO sensitivity, and the distance between the flash and the subject.
For the most part, shutter speed is largely irrelevant in terms of flash as long as it's under your camera's sync speed due to the very short duration of the flash itself. Of course, you still have to worry about camera shake, depending on how and what ambient light is affecting your subject.
In terms of mixing ambient light and flash, I often find it easiest to set the rough ambient exposure with ISO and f-stop for the ballpark, set my flash exposure, and then finally fine-tune the shutter speed to achieve the desired mix of ambient-to-flash.
Looking for more examples of this DIY beauty dish? You can see a full set of portraits shot with the same design here. The design and instructions for this DIY beauty dish are coming up very soon, so hang tight.