When you say you don't see the effect did you do a render and you do not see any effect? Or that you just ran the script and don't see the effect?

From what little I've played with those scripts (I bought the bundle and am using Poser Pro 2010) You will barely see any change to an unrendered item. The full effect is only seen after render.  If you want to see if item has "changed" without rendering you can use the material room.

Before applying the script to an item, open the material room and select the advanced tab and note what materials and shaders are applied.

Exit the material room and run the script against the selected item.

Re-enter the material room and  select the item you ran the script against.

Look in the advanced tab and see what shaders / materials were added to the item.

Other items to note with the "Hybrid Grundge" scripts:

The "Ragdomizer" script replaces the transparency node its own transparency node which may effect the transparency of of a clothing items  (you'll need to do a little work to make a semi-transparent dress remain semi-transparent)

The scripts are installed as byte code compiled (pyc) scripts which makes them "uneditable" Personally I feel is advanced user unfriendly-- you cannot see and edit the original python script and therefore you cannot adjust the strength of the applied effect. What you get is what you get (There are no strength or pattern settings).

The Grime-inizer gives unintended results that looks like mud+gore.rather than just mud / dirt.