If your problem is speed, then that will come with time and lots of practice. How long have you been working on the move?
There might be one point you're missing, though. The SWE Shift, as with all of Erdnase's shifts, is executed and made quicker by opposing pressure of the packets being suddenly released. In other words, both packets are involved in the action, not just the top one that you pull with your thumb and pinky. At the same time as you're doing that, the lower packet is pushed out from underneath with your left index finger, with your right second, third (and possibly fourth) fingers supporting it at the front. Because both packets are being moved simultaneously, each one only has to move half the distance it would otherwise have to. So, the move can be executed twice as fast. Do you see what I mean?
Maybe re-read the description in Erdnase and see if that helps to give you a different perspective.