Love the scooped bs 180 on flat ground. Just do a bs 180 slide but tap your tail while you are going into it. So much fun.
For BS 180 over stuff I learned over milk crates. You could start with one if you want to 180 with the middle of the board passing over the middle of the crate.
Going over the object is a two part motion. The first part is ollieing high enough to pass over the object at a 90 degree angle. When you Ollie turn your back and Ollie your front foot sideways.
With enough timing and force you should be floating sideways over the object.
Once you clear the object drop your front foot down and push your back foot around.
At first you will land at 90 degrees and either stop and slip out or slide the remainder of the 90 degrees.
If you come at an angle you should be facing the object you want to 180. In this case you will get your front wheels over quickly but will need to whip your tail around faster.
Here is a clip of me bs ollieing over a chasm: