I have the Westalee ruler and beginner ruler kit. I am just now using it on my Halloween wall hanging. The key is to have the no-slip material on the bottom of the ruler and to wear gloves. (I use regular garden gloves where I cut the index finger and thumb out so I have fingers free to grab thread and such.)
You align the ruler to the edge of the foot, support the ruler with one hand and the quilt with the other. Then move the quilt - keeping pressure on the ruler against the foot. It takes just a bit of practice to get the hang of it. Now I even use the ruler to do SID. LOVE IT!