In the current version of the Stitcher app on iOS, from the Now Playing page, tap the double line icon next to the Back 30s button. This will expand the playback controller options and give you access to the playback scrub bar, Car Mode, Speed Control (0.5x, 1x, 1.25x, 1.5x, 2x), and the Sleep Timer.
If you tap the Speed Control it will change how fast episodes play until you find the speed you like.