Okay, you have to trim all the excess material off the back side you trim it almost to the seam, If you don't you are trying to shove 3 layers of vinyl in to the channel.
You can take a flat blade screwdriver and a small block of wood, use the block of wood on the paint to shield the screw driver.. then wedge it (the channel apart) Line a old timey can opener. Insert your top, and cable pull it tight, then with the top open and use a block of wood over the vinyl and smack the channel back tight.
If you have the cable in the recepticles and the nut on you should only have the nuts on about 1 turn. I usually don't put the nuts on till after I get the rear cable in.
So 1 trim the excess off the back so you are only doing 1 layer.
2 grease the inside of the channel
I tell you that I don't need anything more than my hands to position the cable in the rear channel. It doesn't take me more than 40 minutes to get the rear cable in and tight.
Excess material being trimmed:
bisections cut
