i only ride surfboards, no skims. so that's all i can comment on.
there is a nice tutorial from herve boure, strapless society, about it. what i took from that is how important it is to bend the foreword knee the moment you take off.
other things that help me is keeping me plus the board very compact. very important in the second half of the rotation, too.
i find it much easier in strong onshore winds. well powered on a 6 m is perfect.
boure says never to grab the board. i don't agree to that but avoiding grabing helps getting a better feel how the board should be angled to the wind.
what i like most are powered backrolls with strong onshore wind and waves somewhere between one and two meters. really pushing you as high into the air as possible and than doing a slow rotation is just so awesome.
for a better chance to land them and keep going it is good not to pull the Kite too far back when rotating. i always try to keep it between 11 and 12. what i find quite hard. in the beginning i did a kiteloop after hitting the water but i don't really like that because i need even more downwind space. at the moment my goal is to change hands at the bar shortly before landing. in the moment i let go of the board i try to get the front hand to the bar and take the backhand off of it for better balance.
another thing i enjoy at the moment are ungrabed backroll transitions. nice to see in the late herve boure videos, too. the good part about them is that you don't have to care about getting the kite in front of you after landing.
i love backrolls. which might have become clear by now
and i find them much easier accessible than frontrolls.