Originally Posted by rigmarol
Take out all your floaters (clips, zinc, screws, rocks, and such) then flux a few times stirring and scraping the bottom and sides aggressively.
Flux first, then remove the floaters. The reason that I say that is because during the smelting process, some tin will leach (this is probably the wrong word) out of the melt. You don't want to discard the tin with the dross, so fluxing first, then skimming will make sure that you've both reduced the tin and separated the contaminants.