I saw a video by Cam Nichols on Zone 2 training and the mistake that most riders make - NOT doing constant pressure on the pedals. Uphill, downhill, on the flat - same power. This means you crawl uphill, and fly downhill, because you're pedaling when others are coasting. It might mean getting lower gears, so you can climb at the top of Zone 2 instead of mid Zone 3.

BUT it's boring as hell. I don't know that I'd bother doing it for midweek 60-90 minute rides. There, maybe do intervals? I used to do a midweek route with a number of hills that made for good hill intervals, with rest in between. Then I'd go much slower on weekend rides.