bubble wrap and pipe lagging ( from BNQ maybe ) are your friend. Just remember to take extra and some duct tape for the return journey. Pipe lagging on the shock, rear mech, frame and more importantly the fork stanctions is always a winning combo.
Bars off and turned and maybe lower against the frame, rear mech, pedals off maybe, wheels off maybe, rear mech off and taped tight to frame. Just don’t leave anything sticking out.
Just tell them it’s an enduro bike ..that way it is guaranteed to get better treatment.( joking )