Bus Barranca-Casma and Casma-Trujillo

I would also really appreciate some information about bus connections in the area. I’m trying to find the timetables for Barranca → Casma and Casma → Trujillo, but I can’t find reliable information online, and nothing appears on RedBus for my travel dates in September.

Are there regular buses or colectivos on these routes? If so, approximately what time do they leave, which companies operate them, and where can I buy the tickets? Is it necessary to book in advance, or can the tickets normally be bought directly at the bus terminal on the day?

Any advice from someone who knows the local transport system would be greatly appreciated!