Not too difficult, once you really get used to the backflip rotation and you flip it so that you've got a good view of your landing most of the time. You might want to try it one of these ways- 1)do a backflip, and then as you come out of the flip twist your legs around and get the 180 in- i.e., backflip 180 or late 180. or 2) do the backflip thinking of the rotation, so by the time you're out of the flip you've already got the spin in- i.e. rodeo five or backhalf.
It helps with both of them if you're pretty tucked up while in your flip/spin.
'The road of excess leads to the palace of wisdom.'  -Jim Morrison