i got no video to show you girls but i'm doing these routes for almost a year now and it works for me

bicycle kick - 25 times x 3 set (rest 1 min in between)
sit up - 25 times x 3 set (rest 1 min in between)
cross sit up (left elbow touching right knee) - 25 times x 3 set (rest 1 min in between)
side crush each side - 25 times x 3 set (rest 1 min in between)

total 300 cruches