If my pattern says:
"dec dec 1 st at each edge"
Should I decrease by using K2tog, or should I use SSK?Also, am I doing it twice?
Usually a pattern says what type they recommend. Does it say anything? Is there a link to the pattern you can share?
It doesn't matter all that much what you use since you'll be seaming, but some people like to ssk on the right edge for a left-leaning decrease and k2tog on the left edge for a right-leaning decrease.
And yes, you'll be doing one at each edge.