Examples

Blurry reflections

sj_pc_tag gets as color a plain reflection node, with the input alpha set to 1 to have the black reflections opaque in the pdc.
In sj_pc_write, Max Depth is set to 1, so that we'll only reflect the first intersection from the camera.

This is the pdc, seen from above.

At reading time, sj_pc_read reads the mrmap in Interpolation mode. Allowing for different Max Points and Radius, you can shape the size of the blur.

Baking hair self shadowing.

We give the hair a flat white setting. The same shader is duplicated for the shadow. In the shadow shader, the transparency is enabled. In the surface, it is disabled, since the successive hair intersections are already managed by sj_pc_write.
Note that the shadows are enabled in the light.
As a result, the color at a given point is the amount of light reaching it, and this is what we bake in the point cloud.

This is the pdc

At reading time, we assign sj_pc_read straight to the light color. Note that the light shadows flag is disabled. Through sj_pc_read, the soft_light will already return the correct amount of light (note also that there is not even a shadow shader attached). Until you don't modify the hair transparency, you can edit the other hair parameters.