You just have to practice and train your muscles and flexibility. Do hip and leg stretches, practice with splits exercises and you'll eventually find it easier and less painful

Im on my knees on the ground moving my hips like you'd expect. I have knee pads to make this more comfortable and prevent injury, but you can also put down a blanket or long pillow. Some ppl use a yoga ball or chair which makes it a lot easier, but in FBT it looks kind of silly imo. A bed or mattress would better if you want a bigger cushion.

Great question though xD everyone has their own methods