I want to make a car cake this week...i tried to cover cakes with fondant...but not really possible for me to take care of the last seam...i couldnt cover even a simple round cake....the last seam of the fondant seams impossible for me .is there any detailed explanation of to do it...or is there a way to do the car cake with buttercream.... please advice..

I've made a few cars with the Wilton car mold (the 3-d cruiser I think it's called). I did two of them in buttercream and one in fondant.

One of my buttercream cars I did with the star tip and that actually turned out pretty cute and was super easy. The fondant one was pretty easy too, but by the time I did that one I was more comfortable working with fondant.

You may want to give that a try (The star tip method). The Wilton car mold comes with all kinds of instructions for different styles of car to make with buttercream. If nothing else, just go look at the package (maybe their website has it too) just for some ideas.

http://www.wilton.com/idea/3-D-Cruiser-Cake
(Mod edited to add Wilton 3D cruiser decorating options link.)