I’m going to try a ganache covered cake for the first time.  Can I do a drip with Royal icing on a ganache cake?  Any tips?

you sure can -- the only tips I can think of is are:

test both on the side of a cake pan to see if it has the consistency you want --

chocolate is temperature driven so you gotta get it just right like goldilocks to get it the way you want it to perform --

and the royal, you can add some corn syrup or water to thin it down to get it to drip -- I would put it in a piping bag myself once I got it where I wanted it --

best ganaching & drippin'  to yah :)

Absolutely. Make sure your ganached cake is well chilled. I’ve piped on drips with royal icing several times. It’s great because you have control with the piping bag. Another great thing, if you don’t like how the drip looks, royal icing is easily scraped off once it’s hard. So you can remove any drips you don’t like. Then pipe again. 

Thanks all!  So I assume the royal icing will dry hard.  I’m thinking to use white Royal icing and once dry use the luminous rolkem powder to make a paint and paint the luminous color onto the drips?

I've never used that powder so I can't comment but yes that's a viable way to do it -- will be very pretty

If I was going to paint my drips gold, I would make my icing yellow. Will be much easier to colour gold then pure white icing.