I'd like to decrease my Magic Trackpad speed by moving the cursor around the screen using 2 or 3 fingers

Rather than "toggling mouse speed" by clicking or tapping somewhere on the trackpad, I'd like to decrease the speed by using two or three fingers to move the cursor. Then when I went back to using one finger it would automatically increase the speed again. That way I would be able to have more precision using the trackpad without having to think about whether it was currently set to the higher or lower speed. Is there currently any way to do this in BTT? Thanks! Love the product!