How to get grease out of my brake rotor holes
I'm sure someone will be able to provide a better answer before too long, but my solution for this sort of situations is baby wipes. I've used them on various parts of bikes (and babies) and they work really well - I think it's mainly thanks to their ability to hold/absorb substances. Things to bear in mind:


We use pampers sensitive and I assume most brands will give you similar results, but I do note that pampers sensitives are fairly flossy in texture whereas some brands like huggies are more cloth like. Hope it's ok to use brand names on stack exchange?
I imagine it may take some experimentation before you find a way of dealing with the shape of the rotor, feeding wipes through holes, getting into awkward corners etc. 
You may also find they leave some floss on, it might be worth clearing that so that you don't jump from the frypan into the fire - the wipes may have not been tested under the pressure and temperature present in disc brake systems. If the floss is synthetic it could melt under heat and become harder to remove.