I use blending mainly, then use the burn tool (on different sizes etc) on certain areas. Occasionally I will blur the base layer of the render then sharpen up main features.
normally i duplicate the render layer so there is four. I desaturate the bottom layer, put the second one on Screen, Third on Overlay or Lighten and the top one on soft light. If it is too strong i would play around with the opacity on the layers except for the bottom one.
I don't really have a set type of effects that I do, it just depends on the type of sig and how I decide to do it. Muck around with different types of sigs, make one which is a bit grungy then fiddle with effects for the cut, make one that's simple and fiddle with effects to see what looks best. It's usually what I do, because it all depends on the background, the quality of the picture and mostly how you want it turn out.
