Nothing a good layer mask can't hide, but for pop-out sigs, or things that don't blend, the hair might look bad.
I am going to unveil a deep dark secret of the trade...after you render something, you can go back along the edges if something is thin and fine and use the color balance to darken it to the proper amount and then belnd it in through with the restof the hair, I have done that, in areas that are too thin, this is almost a must(like where there is a 1/2 px line and in order to extract it, you will either make the line effectively invisible, or else have chop hanging off of it.)
