I have been playing P6 for a bit on this.. I dont claim to know what Im doing... but through trial and error, ive learned that the best result is this that Ive found for what I like..

1 open your texture imgage in a photo editor,
2 convert to greyscale
3 change image to NEGATIVE... (here, the moles and raises on skin always seems to be white(r) now, which is what you want.
4 save and name whatever --just add "bump' to the original file name, and stick it where ever the file name is.... so i know its a bump ...
5 in poser, open the bump, connect to the "bump" or "displacement" nodes. Ive tried both, .. reset the default value to .005, and adjust from there. the default .08 is waaaay too much. use .005 whether bump or displacement...

what I do, is i unattach the texture node in the material room, and play with and adjust the bump on the model before I even attach the texture. this gives me a good render of wht bump with no colors so I can see if it need to be cranked up (value) or down.... the number value is real senitive. my .005 setting will get you to see what i mean, but ive never used anything past .007 or .008

give it a try
;)