Anyone got a sure fire method of getting the cloth self collision to actually self collide appropriately, (without any overlapping or portions of it still moving in and out of itself)?

Never seems to quite do it completely for me..

More polys can help it happen less often, but will make the simulation run longer of course.  I generally just brush around with the P7 morph tool -> Smooth and clean up areas where cloth intersects itself or creases too far and makes the appearance of rips and tears (normal not visible).  If you don't have P7 this obviously doesn't work for you, but you could export the sim'd cloth and it should write out the morphed state, and try to clean it up in a modeling app (probably not worth the trouble).

Increase the steps per frame in the simulation settings and play with the cloth thickness values too.
This will take a lot of experimenting, though, so if you are in a hurry, try what pjz99 is suggesting.

thickness = collision offset maybe?

I stand corrected, you are absolutely right. I don't have Poser open with me sorry :)

Quote - thickness = collision offset maybe?

Thanks for the feedback.   Actually I've been considering putting some stuff up in the marketplace here, and a particular item I'm working on has a dynamic cloth object in the package with a partial layer of cloth overtop an underlying layer. I just hate to put it up for sale when it's acting funky. 

It's an ancient Egyptian style garment that has a sort of loincloth or skirt with a drape in front coming from the waist that hangs over the actual skirt.

Though I could do a version of this with one solid layer of cloth, it really wouldn't be as accurate.