I hate the search function on this site. No matter what I put in, nothing pertains to my problem. I just made a double batch of buttercream and it seems a tad too thin. I thought I read on here not too long ago that you could use a small amount of cornstarch, but I can't find that post. Should I just use a little PS? I don't want it to be gritty. Thanks

yes. powered sugar should do the trick

Powder sugar or corn starch will work.