Depending on how much you have to smelt, I've found that using a cast iron or stainless steel pot over a propane burner is a good way to separate the clips. You take a 1 gallon paint can, drill a lot of holes in about the bottom half of it, fill it with the wheel weights, and then put the can in the pot over the burner. The lead will melt and flow out of the can into the pot, leaving the clips and non-lead weights behind (as long as you don't get it too hot). I prefer to flux the lead at that point and make ingots. When I use the ingots to mold the bullets, I flux the lead a second time. A partner of mine and I have about 500 lbs. of lead to smelt here pretty quick, and this is one of the better means of getting it done in a reasonable amount of time.