Any suggestions on how to thin premade red or black frosting? I have Wilton's ready made frosting and wanted to add some red or black to some cookies and it's too thick. I'm using royal icing to decorate the cookies and the ready made frosting would go on top (either as an outline or accent). I would like the frosting to harden when dried so I wasn't sure if adding water and/or glycerine would be a good idea. Any tips?

Have you found the answer to this yet? Why don't you try adding a bit of water to a small amount of icing. See if it will get to the consistency you want and still harden to your liking.

Thanks for your response. I had to finish decorating these over the weekend so I did add some water to thin it and it worked out ok. Not exactly how I wanted, but ok.