Their lawyers don't need to be experts: It's trivial. It boils down to buying services and rights from other companies you control, such as production companies for past movies you didn't grant royalties for to channel the revenue straight out again.

If the transactions aren't arms length, he IRS and SEC can punch right through them and see that there was a large gift made from one side to the other, for purposes of tax evasion. But for whatever reason, the courts don't give the same protections to private counterparties.