I've tried a grand total of three (!) switch backside flips today, compared to way back when I had done a few shit ones for the sake of psychologically claiming them it seems a lot easier to form now, probably because I have a much better switch flip these days than I had at the time (so while one doesn't necessarily need a good switch flip for switch frontside flip, switch backside flip seems to call for them). On all three of them I could get the form and unlike what I expected my problem wasn't the shoulders (it seems like doing more switch backside 180's recently has helped) but the weight distribution in the air, basically my body wants to keep going and catch the wrong truck, I think mostly because I'm still doing them flat and they don't fold at once, so I need to work on flicking through the board from that position a bit more.
I did a few frontside nollie flips for the first time in forever today though thanks to this thread. Again having a good nollie flip really helps for this one, it's essentially the same thing all the way down to the foot positioning and then you just turn the shoulders and trust.