For speaker wire through the door grommets, a big nylon cable tie works great (big and long - not a scrawny little zip tie). For the front passenger grommet, I disconnected the plastic clips holding the wire to the door sheet metal (to get some slack), pushed the grommet end that engages the door out into the space between the door and the frame, removed the glove box assembly, and was able to push the pointy end of the cable tie out through the grommet opening under the dash. I had to remove the glove box assembly so as to be able to stick my hand in and grab the the end of the cable tie as there is a big white plastic wire connector block that obstructs access to the grommet opening from under the dash.
Rear door fishing in a CC:
I dunno what year truck you have and which audio system, but if you search for "speaker wire color" there are a bunch of posts on the topic.