I've used Ivory soap for years, if I have some air flow. I works great, just put a bar in a quart ziplock freezer bag and beat the heck out of it with a hammer handle. It breaks down into a coarse dust that is then spread across the top of the melt. It smokes slightly, and that smoke is a bit acrid. Not nearly as smoky as parafin or beeswax, and does a much better job IMHO. I tried the wood dowel method, and had to leave the room due to the smoke, plus the dowel caught on fire.
My normal casting flux is Marvelux or the newer Frankford Arsenal equivalent, because I cast without any air circulation indoors mostly in the winter.