Welcome to the Cake Decorators Q&A
Can a fondant covered cake have chocolate ganache drips,
Yes, this can be done. Once you've iced the cake, allow the fondant to crust over before adding the chocolate drips in the usual way. Hope this helps.
I want to airbrush the buttercreamed cake, will the airbrushed colours run when I put chocolate drips on it.
I’ve never done it so not sure. I would do a test on a small section of the cake or on a small dummy to see how it behaves. If you don’t have a dummy, try it on the side of a small cake pan. 🙂