We actually started with a train first - taking the MAX from near our house to the zoo, to the start of the trail portion. To start on the trail, you head out of the zoo parking lot and cross the overpass over Hwy 26; you actually are basically walking along an on-ramp to get to the trailhead (but do make it onto a nice trail before you're on the freeway).
Before you know you feel like you're in the middle of the woods - although you can see still peeks of the city between trees.
Part way through the hike you go through Council Crest Park, the highest point in Portland for some lovely views of the city.
After Council Crest, there's is a choice between the trail and a shorter alternative urban route. The signage here was less clear, but I think we ended up on the main trail route. There are a few times throughout the excursion where the trail goes across or temporarily on roads, but most of the time, there is clear signage, combined with directions from the 4T website, that made it readily apparent where to go.
The hike portion overall is about 4.5 miles, and I believe it took us around two and a half hours (including stops for photos and checking directions). I don't do a ton of hiking (but should - we don't live that far from these trails!), but figured I do enough running it'd be relatively easy and quicker than that - not so much. You're on groomed trails, but there are definitely sections that are steep - both up and down - and you do need to pay attention to your footing, stepping over roots and rocks and such. Although my mom doe a lot of walking on paved park trails for exercise, I would definitely hesitate to bring her on these trails.
Eventually the trail leads you to the OHSU campus. (Another spot where both signs and directions were slightly confusing). You go through one of the buildings to the tram, which is free for the downwards portion. (But there are limited hours of operation, so be sure to check before you go! We ended up with only 30 minutes or so before closing after the trail taking a bit longer than anticipated.)
At the bottom of the tram, you hop on to the trolley. The 4T directions specifies which station to get on, but there's actually a nearer station right at the bottom of the tram, which just puts you on one stop sooner (there was another couple doing the 4T that we overhead asking a tram employee about it, and it's the nearer station they were directed to).
After getting off the trolley in downtown, you hop on the MAX train back towards the zoo. We made a pit stop along the train route for dinner at the Hot Lips Pizza by Providence Park, then continued on the train, past the zoo and back home.
Doing the 4T trail is a great way to see a lot of the western side of Portland in an organized fashion. Do make sure to allow plenty of time for the hike, and account for the operating hours of the tram. Enjoy all the sights!