A Bullflip is basically a nollie gazelle under 720 Hardflip.
1-Set your feet up as a nerd flip with the front foot cured off the nose to get the underflip and the back foot on the tail much like a shove-it.
2-Pop the tail hard! This is important to get the board high so your underflip works.
3-When the boards sort of in the air your front foot will need to get under the board and kick it out to get the 720 spin.
4-The board will spin differently every time, so make sure to gazelle flip it(so it spins like a 360 flip).
5-Jump way high this helps to give the board time to spin.
6-Follow the board as it spins in a random way and may go flying in one direction,just keep trying you'll land one.
7-Wait until ether you see the griptape and land it.
Once the decks been popped, kick harder makes it spin more but also makes it harder to land.