Advice using fill flash for indoor/outdoor pictures

Hello all. A few weeks ago I witnessed a photographer snapping up pictures
for a wedding. He was using his flash for all of his pictures, regardless
if they were taken inside, outside, in the sunshine or with the sun blocked.
I hate using the flash because I find it very difficult to use. I've
started reading about various techniques posted on peoples' webpages but
found no beginner's guide type of article on using a flash / fill flash. My
question is, all things being equal, can someone describe the proper method
of taking pictures using a flash. I have been taking pictures here and
there for many years using the following equipment (which is hopefully on a
long term loan): Nikon F2as with all major Nikkor lenses (favorites consists
of 85mm f2, 135mm f2.8, and 50mm f2, 35mm f2.8). My flash is a Image
TB-100. It has 2 flashes (1 can be angled) and a wide, normal, and
telephoto dispersion. This flash has a lot of settings but I started
experimenting using the manual setting. For example, I took some pictures
using the full flash power in an outdoor setting with partial cloud
coverage. I noticed that my subjects' legs came out well but their faces
were too bright. I wonder if there's some kind of table I can use to adjust
the flash's settings. For instance, assume that my camera meters at f8,
125s in partial sunlight at 10ft (for example). Is there a table that can
tell me what to set the flash at? E.g. 1/16th power, or 1/4 power or full
power? That photographer made it seem so easy ;-)

Regards,

Domenico