I would invest in a shoe or boot that matches the height of the aircast, so when you walk your hips remain level.
All the time I've had the boot I've been doing exercises with my foot, from basic toe wiggling through to more complicated propreceptive exercises, and I still suffered my PE due to lack of circulation. Keep it moving as much as you can.
Massage helps promote better circulation (I did my best) and reduces swelling. It also helps maintain proprioception so your foot can perceive where it is in relation to your body.