This is a stage-specific trophy and can only be obtained on: Mermaid Falls, Stage 2.
The Techno Grunts are the little bipedal gator grunts that waddle around the factory floor. I'd suggest waiting this until you have the Harpy Dance as it helps with part one and two. For the first part, there are two grunts to worry about, so you can either sneak by them normally or just flap your way over them. The second and third parts are where it can get tricky. With the Harpy Dance, you could easily just flap your way from the lower left all the way to the top right by zig-zagging through the factory floorplans. The third part is the trickiest though, as you will not be able to bypass the two grunts that patrol. Wait for the first to get far off the screen, then follow behind and quickly fall into the first hole. Let them pass over you heading left and then quickly run to the right where the Snake Charmer can be found. There won't be any other grunts left, but you won't get this trophy until you slide down the chute.