For beating the World record you'll get a 25€ discount code from kendama.cz.
One Bird is enough to get the bronze badge. For silver and gold the trick changes to Bird over the valley. To get the silver badge you must do 5 consecutive Birds over the valley, 20 for gold. Each landing on a rim counts as one Bird over the valley. You can only do hops, no earthturns over the valley! So you go back to back from bird to nightingale, nightingale to bird 20 times without dropping it. Good luck.
More about gradings at Grading.