Can someone give me tips on keeping black piping from bleeding. Its going to be a buttercream frosting but if I do it the night before Im afraid the fridge will cause the black to run a little. Is it better to use buttercream or piping gel for the black piping?

Its best to use royal icing if possible. It dries quickly enough to not bleed. If I can't use royal, then I wait to put the black on until the last possible minute.