There are a few articles online, though I learned to paint in oils
before the internet came along, so I'm not sure where they are. You
might try some of the tutorials
HERE.
I'm sure others here can guide you to some fine online tutorials. I'll
have one on my own site eventually, but I don't have it there yet.
Personally, I like the natural sheen of oils. The trick is to
spread the paint as thinly as possible, while still attaining good
coverage.
That helps it dry faster and it also dries to a more dull sheen. Skin
actually has sheen, so I feel that oils give skin tones a natural,
skinlike feel. You can clear coat it, but becareful not to make it too
flat. You'll notice that your skin doesn't have a layer of dullcote
over it.
You can attain good skin tones with a basic set of paints. Titanium
White, Gold Ochre (or Yellow Ochre, if you can't find Gold Ochre),
Burnt Umber, Burnt Seinna and maybe Cadmium Yellow and Cadmium Red.
Blue Black, and French Ultra-Marine Blue are also useful. My mixtures
are a little more complex than that, but the resulting tones aren't all
that different really.
You might do a little poking around here, with the search function. The
subject of painting with oils has been discussed many times, and
there's a wealth of info right here that might be useful to you as well.