Should the pan/griddle be oiled? I'm assuming a non-stick pan wouldn't be wise as it would be damaged by scraping with a stiff metal spatula.

Yes. Even in my ultra seasoned cast iron. That's why I tried my nonstick which was dumb because to get that crust, the pan needs to be hotter than is safe with nonstick. The downside is the burgers will never be medium rare, but I'm hoping to get them to medium by increasing the size a bit. I think it's an exercise in futility since the crusty exterior is the thing. I still want to try though because I'm that stubborn. I really love a double double from In-N-Out. I have one immediately upon landing in San Diego to visit family.

Phil these are quite different from your normal burger. Kenji was working on a DIY In N Out burger. You literally smash them while they cook, so you have to scrape them up. In fact, Kenji does a whole thing on the DIY Animal style burger that is a fun read. Here's the link to the original smashed burger article though.

http://www.seriouseats.com/2014/03/the-food-lab-maximize-flavor-by-ultra-smashin.html

I didn't answer your question fully. I didn't oil my cast iron pan, but it's really well seasoned. Even scrambled eggs don't stick to it. The original recipe on seriouseats.com specifies not greasing the pan. You'll need to make sure your burger meat contains enough fat. Kenji suggests 25% fat. I found only 20% so I added some ghee to bump it up.

Thanks!