Well... usually, if you're stuck, you could always try using everything on everything. That should get you the hint what to do next 
If you're seriously stuck, though...
You're right with the molten metal and the rags, but would you want to stick your hand in there? You're going to need some way to extend your reach.

If you're seriously stuck, though...
Spoiler
You're right with the molten metal and the rags, but would you want to stick your hand in there? You're going to need some way to extend your reach.
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