The bulk of rattles and squeaks in my Kia's are from the rapid assembly plastic snap fasteners that the assembly lines used to speed things up nowadays. Interiors that at least use SOME screws in strategic places dampen jiggling sounds better than any plastic fastener ever will. But putting in more screws takes time and more time ups the cost to produce the car and here we are !!!
What I do:
I had some left over 1/2" hard foam flooring tiles. When I cut these and using my genuine "Harbor Freight plastic interior body tools", I wedge them into spots where the noises or rattles seem to come from. This put outward pressure on the fasteners and they have nowhere to move when I go over a bump. The hard part is finding and gaining access to that sweet spot to deaden the noise.
Another neat idea. Piano tuner use little rubber wedges to deaden strings as they tune a piano. My friend gave me a bunch. You can also find them on the web in different sizes. I can get these into some really tight dash spots that rub and squeak, and cut them off with an Xacto knife. Result: no squeak...!!!!
Only on a Kia:
I had a 2003 Sedona that had a wicked creaking noise when I would turn uphill into my driveway, flexing the body. After tearing the car apart I found a broken spot weld between the B pillar and the floor, right where the sliding door closes. A FREAKIN' BROKEN WELD !!!!

The dealer apologetically rewelded the spot.
Now Kia's come a long way from 2003, but I have a 2008 Suzuki SX4 that's also built "on the cheap" and I can tell you....2 yrs. no squeaks and rattles, in fact not one mechanical problem to date. Maybe I'm lucky or do the Japanese still put them together better...??? Makes you wonder....