I'm not super experienced, but I've done it enough to know that a few test runs are your best friends. Hiking/backpacking/fishing trips in July to get your gear list ironed out are a must. Start hunting with bear trips in August to further dial in your gear and best practices. You're going to have too much crap your first couple trips. Whatever you don't use or touch, get rid of it for the next trip. The guys who are dialed with their gear have lists as simple as a notebook or as complex as excel spreadsheets with individual weights, etc. I feel like having a gear system that is tried and true is possibly more important than where you go, especially in Washington.
There are a ton of threads on here with really great info, but the backcountry threads have definitely not been as popular as they were a few years ago.
A couple good ones:
https://hunting-washington.com/smf/index.php/topic,94500.msg3432651.html#msg3432651https://hunting-washington.com/smf/index.php?action=profile;u=10779;area=showposts;start=45Once you're ready to head out, pick a wilderness area or a trail system that gets you into the woods a few miles and hit the trail. For the September rifle season, you need to be within the boundaries of the wilderness areas listed in the regs. They'll all be pressured and you should expect to not be alone. You should plan to have the best armed backpacking trip in some of the coolest scenery and settings you'll experience. Shooting a deer is a bonus. Some people do it every year, some people never kill a deer. The experience is worth it either way. Your best odds of shooting something are probably a bear trip during berry season.