OK, I'm at a bit of a loss, I don't have an Android phone in front of me, so bear with me: Tap the Shape icon (triangle/circle) in the top toolbar. That will open a menu of shapes. Tap any one of those and the Touch Slide, with two finger guides, will open along with whatever shape you've chosen.
I use one finger from each hand to move the guide around but do it however it's easiest. You can resize the shape by spreading pinching your fingers on the edge of the shape and move it around the canvas with the guides. Then, when you're ready to place the shape permanently on the canvas, just "stamp" it with a double tap on the shape.
Let me know if I've inadvertently misled you and that doesn't work. Or if there's anything else you need.
I just realized that this feature isn't yet in the Android version of Draw. But, hang in there... our plan is to develop these apps in parallel with similar features.
Sorry for the misinformation.