All,
Just drove from Ft. Collins to Seattle and back for Christmas with my wife in her 2001 Jeep Cherokee.

I have some things to share you might find useful.

Route was I-25N to I-80 to I-84 to I-82 to I-90 to I-405 in the Seattle area. (I chose NOT to take US287 between Ft. Collins and Laramie as the westbound was at night an the eastbound was in windblown snow probably across the road conditions)

Roads going west were quite ugly. Wyoming was about half ice-covered with 45 mph speed limits.

Utah and Idaho had middling to hard rain (better than ice or snow). Overnighted at Boise (Comfort Suites at the airport is recommended :-) and the wet roads froze to ice overnight.

Boise, ID thru Oregon to the Washington border was 90% ice covered roads turning to heavy fog around Pendleton OR. Drove across Oregon mostly in 4WD Hi at 50 mph max. There are some really long, steep (scary when icy) hills on the interstate thru Oregon. Truckers were chaining for the hills and leaving the chains on if the roads remained ice covered. This created a very noisy, choppy ice surface to drive on. (like a washboarded dirt road)

Snoqualmie pass and the west side was dry going out.

Return trip was dry and fast because we left a day earlier than hoped to run in a clear weather window. Had a few icy spots in Wyoming where the snow from the day before was being wind-driven onto the roadway creating surprise icy spots. Wind in Wyoming was 20-30 mph quartering tailwind. (It's ALWAYS windy in Wyoming)

Some in-car techniques that worked well for me-

I wore Underarmour synthetic underwear that goes down the leg so wasn't sitting on seams as I would if I'd been wearing briefs.

I wore BDU pants. I kept nothing in rear pockets to sit on. Kept a baggie with : eyedrops, hand sanitizer, ibuprofen and chapstick in a thigh pocket. Used eyedrops at each meal stop. Wallet rode in other thigh pocket.

Wore a cotton longsleeve shirt with two front pockets. Kept pen, other hand sanitizer and notecards in those pockets. Heavy coat was right behind the front seat where I could get it but I didn't drive all bundled up.

Wore insulated, gore-tex winter boots to drive in. They were too hot! I wasn't out of the car much but they would have been great if I'd been chaining up or digging out.

Wore padded elbow pads bought in a sporting goods store. This let me rest my left arm comfortably on the door sill and my right arm a bit better on the center console. I didn't get to drive like this on the way west due to the icy conditions but did so on the way east. While the pads are designed for impact and could be softer for this application they worked well enough to use again.

I carried chains but didn't need them. 4WD Hi was needed much of the way though. A 2WD pickup might have needed to be chained. There were several 18 wheelers jacknifed into the medians on the downhills in Oregon and others not making progress uphill. One semi was unable to leave his parking place in the rest stop because he'd settled into depressions in the ice and couldn't get out.
(no chains)

I used a digital scanner pre-programmed for all the states, counties and cities along the way. This was to keep track of snowplow reports and crash reports. This worked very, very well as I could learn that the roads near Boise were icing up while we were still an hour away. Also heard the Wyoming snowplows doing their jobs and reporting conditions where they were.
(My screen name was chosen during a discussion about whether CBs are useful or not. I posted a long writeup about that. I had CB channels programmed into my scanner but didn't get useful info from what I heard. Trucks I was following were asking oncoming what conditions were like. They were getting reports that were 8-12 hours old and that far away from us. Not likely to be valid. And the usual f-word laced discussions weren't something my wife wanted to listen to so CB19 was locked out much of the time.)

I've made the drive each way several times but never in winter. It was an adventure!