RiverRider. I agree. Marvelux is a lot better to work with than any wax. An even better one, IMHO, is LETS. They have two types. I forget what they call it, but one is a special flux for mixing antimony alloys. It smokes like he!!, and stinks even worse, and after you're done, you have to flush out the empty pot with water or the pot will rust badly. But boy, does it ever work. The regular LETS flux is a bit better than Marvelux, but both work well.
For what it's worth, when you are done casting, and you've drained evey last drop of lead from the pot, and let it cool down some, fill it with water and set it at about 3 on the dial. Let the water come to a boil and scrub it out with a stainless steel brush. You'd be surprised at how clean that pot gets. I do it about every fifth time I use the pot. Helps keeo the garbage out of the melt.