I made a batch of Sugarshack Buttercream last week and it is in plastic containers. Do you remix your stored buttercream? Will is still be nice and fluffy? I've always made a fresh batch in the past and never use some that had been stored.
I don't know about Sugarshack's recipe, but I remix mind all the time. Even if it sits for a few days before I need it, it separates a little and rebeating it helps it to be more smooth and creamy.
Yes, a good stir w/a wire whisk by hand usually is enough. Use a figure 8 motion for a couple of minutes.
I stir mine up with the spatula, because I never used stored bc to ice a cake. I always make it fresh. Just think it tastes better. I'll use it for a flower or writing etc.. but if your going to ice a cake you should remix and might have to thin with corn syrup to spread easier.