William Johnson submitted this route which starts off Hwy 97 south of Oroville, WA, and ends on top of Mt Hull (4619'):
Trail starts two miles south of Oroville WA at the Whistler Canyon trailhead parking lot. Trail gains 3300 foot in elevation. Whistler Canyon is a 13 mile section of the Pacific Northwest Trail. The 13 miles is all uphill to the Wilcox Mountain trail head on top of Mount Hull. Lots of flooding in spring and trail can washout in places. First 5 miles climb steeper and pass Black Diamond Lake Trail and McDonald Trail. At 6.6 miles there is a picnic table at a huge lookout in the provided picture, good place to stretch and snack. The rest of the trail is more runnable and rolling but still uphill. At mile 9 the trail branches to the Wildhorse Trail to the right and you have to look for a Wildhorse Spring trail sign at mile 10 that goes left uphill that can easily be missed. Can get very hot in summer with rattlesnakes. Moose, cougar, and bear frequent this trail due to many artesian spring fed small lakes. Many downed trees and thick brush can obscure trail.
Some more info is here: https://www.wta.org/go-hiking/hikes/whistler-canyon-trail