Drosen, haven't ridden west beyond Jewell Junction/Elsie. It's got a decent shoulder that far, tho heavy traffic. The new ODOT bike map shows it as having a less than 4' shoulder from Jewell Junction to about 10 miles west, then 4 foot + to hwy 101.
An alternative, albeit a considerably longer one, would be to use 26 to Jewell Junction, take 103 north to Jewell, then 202 west toward Astoria, then at Olney take the Youngs River Loop Rd. to Tucker Creek Rd., then south on Lewis & Clark Rd. to Seaside, and there to Cannon Beach.
Here's some maps - see Astoria to Vernonia detail section map 4 in particular:
offhand I'd guess it adds about 20+ miles or so, but much more pleasant and very low traffic compared to hwy 26.