Are there any tips of the trade I should know in order to use an Impression Mat on Buttercreme??

Thanks!

oh...also, do I need to prepare the mat in any certain way like I hear for Fondant? (Spray oil, cornstarch...anything)?
Thanks

I;ve had good luck when I've let the buttercream set and become more firm.

I just let the icing crust for about 5-10 minutes and the impression mat works great.