Reply to "How Long to Store Fresh Icing"

First time poster.  I have searched this site using all the key words I could think of and came up empty.  This was the closest to what I needed.  I also have trouble figuring out how much icing I will need for each group of cookies.  When I bake I use multiple cookie cutters so I have four or five different shapes that may not be for the same event.  When I make icing, using merengue powder, I make with two lbs of confectioners sugar.  My problem comes in when I don't have time to ice all of anything at one time.  I have leftover flood icing in my bottles, with color mixed in, that I want to continue to use until it is gone.  All that said, my question is with the flood icing color settling between uses.  Any ideas on an easy way to "remix" it in the bottle? I don't want to pour it into another container, mix, and put back into flooding bottle. I lose too much icing that way. I don't know of a stirring tool thin enough and long enough to be able to remix in the bottle.