ok here is a mini tutorial. a different example.  here is the original render out of poser. 

now lets go back in poser. on the front light i made the specular black. so when i render it out i dont get the specular from the front light.

now i turn of the whole back light. i make the front light black for diffue and white for specular. so when i render it out i will only get the specular from the  front light. i also open a python script . with the script we will make every blinn smaller or bigger.

now all we have to do is go in photoshop and combine the two renders together. the specular render goes on top of the diffuse render and the blending mode is set to ''screen''.