Heres my quick guide on how to remove rear rattles
I find the little compartment lids on the side panels tend to rattle so place some dynamat in the little plastic hooks on the front where the lid clips onto and at the rear of the lid there are some upright plastic bits if you look carefully. No rattles there anymore.
Also behind the center armrest between the front seats theres a compartment for something, that was rattling, 2 layers of dynamat there and job a good un.
I ran about 3-4 layers of dynamat along the window line just under the interior plastic just in case.
Took the seatbelt assembly off and placed dynamat there and bolted the assembly back on top.
Place 1-2 layers of dynamat where all the panels clip into the car to make the clip tighter. Also place some dynamat where the rear boot area panels screw into the car.
On the boot lining panels I also put dynamat on the plastics and along the edge of the plastics to make them heavier and less plasticy when you tap them.
The parcel shelf I put some insulating tape around the hooks that clip onto the car(not the hooks on the strings) to make it a tighter fit. Also put some insulating tape around the rear seat hooks as they were rattling a bit.
Heres some pics when I was doing it.
I added 3-4 layers dynamat strip all long along the window line here right up behind the plastic upper panel that hides the airbag after taking this pic. There a metal hook that stick out here too just under the window, I ran the dynamat over that just in case.
You can see here I've dynamated the cables down and placed pieces of sponge behind the cables.
Hope that helps.