As far as frozen bushings go I just bring my skateboard inside with me during the winter...
I couldn't imagine leaving my board "outside" (in car) all winter.
I've been skating transition a lot recently. Temps have been in upper 20s and low 30s. I've been wearing under armour cold gear as full base layer. Over the UA, I've been wearing on lower body, army/BDU shorts, pads, and knee high socks (full-on 80s style), and on upper body, long sleeve t-shirt, t-shirt, and windbreaker (elbow pads over windbreaker), and gloves. On head I've been wearing a knit hat, and on really windy days, I'll add an under amour cold gear hood/mask. This has kept me plenty warm. That said, more than three people ramp and you start to get cold waiting for a run.
Street skating: All the above, but no pads, and pants instead of shorts.