bu what is crumb coating , meaning coating the cake so you have no crumbs, but i dont get it so after the you let it stay and then coat it again?
Because i only coat it once.
Crumb coating is a thin layer of icing you apply to your cake to "catch" all of the crumbs that may come loose while your icing your cake. You don't want those crumbs in your final product so you first cover it with a thin layer...let that set...or "crust", then add your next layer of icing which would be thicker. Unless you get crumbs in your whole bowl of icing...you should be covered on not getting any crumbs in the final icing.
Hope that doesn't sound too jumbled. LOL
^^^^^ explained it very well.
Good explanation from PP. Just to add that I only do crumb coats on crumby cakes. I don't do them on pound cakes or WASC.