Keep a pad to take notes. As a backpacker, you started with all your food and fuel. But on a long bike ride where you are resupplying every few days, you do not want to walk out of the store forgetting anything. Keep notes of what you need as you realize you need it.

In 2014, I started at Astoria and went to San Fransisco. Some of my notes, thoughts and observations are at this link:
Southt to North Pacific Coast Highway Concerns

My info is of course five years old by the time you go next year, but I suspect that 90 percent of it is still valid. You should double check locations of state park hiker biker sites on the state websites to verify that they still have hiker biker sites where you plan to go.

They changed the software for this website a few times since I posted it, so the photos are a bit messed up, but you will still figure it out.

And bring a cork screw, you do not want to have a bottle of wine in your pack and then realize that your cork screw is at home.

Test your panniers and racks on the bike with a load around home to make sure that everything works in harmony.

You will get it figured out pretty quick, you are going to have a great time.