I've done them very easily. (I have TC3 so this may not work for you if you have 04) Open CMP. Find a nice dirty loco and open it for edit with CCP.
Untick the 'engine' part and remove the horn and enginesounds. Now change the enginespec to the default wagon one (kuid:-1:42004201) and save it. Now your loco will be a piece of rolling stock with no sounds and no abilty to move on its own.