I archery hunt for Roosevelt elk on the Oregon coast every year and have helped with rifle hunts in the same area during November. On elk all the time and have killed a few since moving to OR from South Carolina.
Your thinking and approach sounds great so far.
Are you sure of the month-- what tag do you have/plan to buy exactly? You said your hunt is in October, but he Oregon Coast Elk general rifle seasons are Nov 9-12 and Nov 16-22....
Most people glass clear cuts, find a herd and hope a bull is still with it. They will tend to hang back in the timber while newly pregnant cows feed and loaf in clear cuts. Many of the bulls will be back on their solo routine. If the weather is bad, they will be forced to feed and you can find them popping out into clearcuts to seek higher quality food. Other good options are, seriously, gravel roadsides and hidden skid roads. On the coast, these are your secret meadows because grass grows there. Look for roadsides or logging turnouts where elk have been bedding and spending time. You'll know it when you see it. I say this to make a point: you don't NEED to go deeper in order to be successful. When glassing, be there at first light and last. A bull might pop out to feed for 5 minutes and be gone. Luck drives whether you will see him sometimes...
Another tactic is spot and stalk in the dark timber. Bulls are going to spend most of their time hidden away in the timber. The rain softens the terrain and creates white noise, so you have white noise to cover your hiking and can sneak up on them in their beds/travel areas. Look for timber beds and heavily used trails.
Local lore is that Roosevelt elk feed on a 6-7 day pattern if not disturbed. Not 100% of the time but pretty good to think about. This means that if you see them in one clear cut on Monday, they are going to feed there and eat a lot of the available food and then move on to another cut where they can eat new growth there. Repeat every 6-7 days.
Don't overlook reprod. It is horribly wet if raining, but inside 10-15 year old reprod you can find a ton of lush grassy mini-meadows and these Rosies can spend a lot of time there because they have food, water, and cover. It's nasty going in there, but can be rewarding.
Again, depending on the area you choose to hunt, the human dimension will likely be your biggest challenge. There are TONS of people going for a big elk with big rifles and they are not afraid to shoot across canyons, road hunt, disrupt, etc. There are good hunters out there. But expect the worse, unfortunately.
Hope some of this was helpful.
Good luck!