Engine back from machining! What next!

Yup bought some tonight have to stop and pick it up when they open! Ive got a pretty good idea of what i need to do here. Ive got all the supplies and tools i need. Now ive seen conflicting videos and posts about what to coat the pistons with b4 install Some say light oil others say WD-40 what do yall use?

Best stuff I have found to keep surface rust from coming up is Remington gun oil in a spray can. It is called "Rem oil". Definately get it on machined surfaces and hardened parts like valve springs.