I use several things which, as mentioned in the last post, all smoke. The smoke can be alleviated to a large extent by lighting the fumes, the flames consume the smoke without effect on the efficacy of the flux. Look in your yellow pages for honey producers, You can usually buy raw beeswax from them for a good price, and a couple of pounds will last a long time unless you are casting commercially.
You can use beeswax, parafin, synthetic lubes, crisco, or just about anything greasy. Many years I bought some synthetic beeswax at an army surplus store and found it is of no use other than as a casting flux. I also keep bullets which were sized and lubed and found to have defects, there is enough lube in the grooves of 3-4 of them to adequately flux a pot.
Contrary to another post, there is absolutely no hazard in introducing something cold into the pot of molten metal. That is precisely what we do every time we add another ingot to the pot! The hazard is introducing water below the surface of the melt, it will flash off as steam nearly instantaneously and cause an explosion.
For my purposes I didn't find anything with Marvelux which gave me offsetting benefits to the disadvantages I have found with it, including cost.