I'm no expert but I'd use assembly lube on new cams. Reassembling used cams I would just use oil. I may be wrong but in my mind the assembly lube may help with a little extra protection during the initial break in (first 10-20 revolutions).
I never, ever use assembly lube when doing cams. I just put some oil on the cam journals, pour some on the cam before I put the valve covers on, and let it rip. I've never had an issue doing it like that. I've done a few sets that way.
The reason for the question is I watched the Ford tech video and they say to just put oil on the cams and the journals. Today I asked a question on the FRPP site and the tech guy said don't forget to use assembly lube?????
Oil pressure builds in seconds, I wouldn't worry about it. Put some oil on the cams, put your covers on, and drive the car like you stole it. There is no need for assembly lube or break in time.
If the motor was new or just got back from the machine shop, I would use assembly lube. But a cam swap on a motor that's been running, new or used cams I'd just use oil.