Scrape as much fat off the underside of the skin as possible, if the birds are at least split, the worst of the fat is easily accessible.
Dunk into simmering water for 15-20 seconds, and them immediately in ice water, repeat once.
I also often use a little baking powder, it doesn't take much, it works best at high temperatures. Note: The baking powder trick will only work if you DON'T use any acid.
I dry the skin with a hair dryer that's dedicated to that purpose only.
Edited to add: The reason I like to at least split birds instead of spatchcocking when I want to ensure bite-through skin is because some of the skin often overlaps and bunches up when spatchcocking, which creates problems......plus it makes it easier to access the fat underneath the skin
~Martin