For blind side switch ups, think about spinning a little more when you go onto the box/rail. Like land almost like 100 degrees and you'll feel yourself turning and as soon as you get to like 130 or so, turn your shoulders and pop, you'll get it. Practice on flat down boxes, best way to learn.
Maybe partying will help
You need to turn your head more. Wherever your head is (where you're looking at) is where your body will end up. Once you're ready to switch up, pop off the rail, turn your head, spot your landing, then turn your shoulders to whip your body around.