Yes, you talk to your lawyer.
It doesn't take long and can be done with minimal lawyer time. There are around 15 families of IP rights that need to be either assigned or waived specifically. There are also location-specific regulations that need to be followed. You need to specify consideration of payment, purposes and allowed uses, combination with other works and media, assignment and transfer, exclusivity, duration, choice of governing law, and so on.
Your lawyer will then prepare the document.