I would like to know, can us use a can of duncan hines chocolate icing, melt it in the microwave and pour it on the cake?

I'm not sure where on here I saw it and I even saved the photo but I have too many. Someone did a beautiful cake with chocolate ganache and they said it was made with Betty Crocker Pour and Frost icing! I'll see if I can find it for you.

Yep, you can do that. Stick it in the microwave for about 1 minute until melted and smooth then just pour it over your cake. Did that with a Boston Creme Pie recipe one time turned out pretty good.

Regards SugarCreations...

Thank Yall!!!!!!
I will do that....
Can I still decorate the trimming with buttercream icing after it gets a little hard?

Don't see a problem with that. I would set it in the fridge for a few minutes to kind of let the icing set up a bit before I started with the buttercream. You may have to smooth out places where the icing does not cover but it should cover well. Good Luck..

Regards SugarCreations...