can anyone tell me how to crumb coat a 3d stand up christmas tree???

You can always do it with your hands. Mike McCarey has a great DVD that he sells of how to make a car cake (any car shape), and he gets a perfectly smooth crumb coat by warming the buttercream slightly..just until it's goopy (but not curdled)...and then just smooths it on with his hands. He does a few thin coats of it, refrigerating in between to set it. It works great.

I'll second SweetDreams_DK's suggestion. I have the same Mike McCarey video and I have used the technique very successfully on all of my sculpted cakes since then. I would add that this is going to work much better if you use an all butter buttercream.

I too use my hands anytime I have a 3D cake which requires small crevices etc..Much easier....