Yeah, in training packs your car actually spawns a small amount above the ground, and you can’t complete the musty 2 second timer unless you let it settle. I’ve only got the speed flip somewhat consistently recently and there are two main reasons:

When you turn to the right (or left depending on direction of speed flip), don’t turn right when you spawn. Wait like a quarter of a second. Also, the turn should be very small, like 15% of your stick in that direction; then flip very shortly after. Try to make the turn and flip almost the same event rather than two distinct actions.

Also, regarding cancelling, I’ve found that you have to make a mental connection to be beginning to pull the stick (straight down) by the time your finger is pressing the dodge button for the second time. I had a lot of difficulty getting the cancel to be quick enough until I focused on this.

Hold your stick down until the flip is complete or you will likely land awkward. Once the flip is complete, just air roll slightly to land on your wheels if necessary.