Well since I have Poser 7 I'm not sure whether these will work, but here goes on the list:

1. Pozers Little Helper: http://home.online.no/~kjellil/Index-AllStuff.htm

        Morph obj in an ext program, import into PLH and it will generate INJ/REM files)

2. Morph Manager and CR2Editor: http://www.morphography.uk.vu/dlutility.html

        Morph Manager can edit Poser files to add/remove Injection Channels and does numerous other things... CR2Editor edits Poser files (cr2,pz2,pp2,hr2,pz3, etc...)

3. P5 MAT Writer: [[Works in Poser 7, so it might work in P8]] http://ixido.com/shnarf/index.php?topic=53.0 {{Scroll down the tutorial to where it says "P5 MAT FILES" the link will be in either blue or green :) }}

Those are what I use, Pozers Little Helper to make INJ/REM files, CR2Editor to edit the INJ/REM and MAT files, and P5 MAT Writer to make the mat files... hope this helps :)