The route from the east is not that long, but it feels much longer. I tried it on the way back, the wrong way around, but I suppose it works as well from the other side. Routes have this kind of feature, they work both ways, often enough.
Starting at Dalmunzie, just off the Glenshee road, up the old railway track to the ruins of Glenrochsie Lodge, where the path to Glas Tulaichan branches off, the nearest Munro on that side. Then across a ridge with deep heather and grass, rough and full with animals, lowest point about 700 meters. Then drop down to Daidhu, the point where I hide my bicycle when I come from the south. It takes more than two hours just for this part, at least, plus the useless hill. This is probably not a realistic option, if the goal is just to get to the loch as quickly as possible.
It is long and arduous, but it has its features. A series of swimming holes, waterfalls, and cataracts along the Glenlochsie Burn. A meadow with helpless birds on the ground and red kite hunting overhead. I walk right through them. On the path: Piles of sheep feet, cleanly hacked off. Daidhu always has the air of death. See that, lambs? That's your future. But I'm the enemy, sure.