It can look great if done well.
Not a technique that all are happy with though.
http://leadadventureforum.com/index.php?topic=13306.0
Nothing like a theory that splits people... haha!
In all serious I didn't know there was a tutorial... I just bought some artists oil colour at a discount and tried mixing and modding.
Apparently you're supposed to use Windsor & Neutron as they have the best paint. Or pigmentation. Or both. Or neither!
Anyway I toyed around with my oilies a bit more and tried painting some more trolls with them:

Several things went wrong. Some went completely bonkers.
For instance I failed to appreciate that you cannot touch the miniatures for days after painting... so now they've got black marks all over where I've worn off the paint with my fondling.
Secondly (not related to oils) I wash a part of the left trolls leg that I thought was cloth... so when trying to make it look like the skin colour again it was impossible. Also down to my colourblindness. I was unable to find out what colour I had used to paint the leg with. (I used an acrylic base).
So now one of the legs is green. But what the heck. Trolls and hygiene.

Even more obvious tear off's. A large fingerprint is really all that's missing.
But yeah, well, it took like no time to do this as I could just continue working with the colours on the model. It was a bit difficult to control though...

A fight broke out with some dwarves that are also on my painting desk.