Best gloves for handling cast-iron (and grilling?)

We might not be able to help you. Personally, I use the OXO Good Grips oven mitts. The have a silicone shell so they are spill-proof and steam-proof, and they have a liner made of quilted cotton you can wash separately. (They are a little small for my size L man’s hands.) They are ”heat-safe” to 600 degrees F, which I suppose means they won’t catch fire or melt below 600 degrees. But that doesn’t mean your hands won’t get uncomfortably hot in 600 degrees; it will eventually. Insulation only slows down the transfer of heat, it cannot block it completely. 

So what that means is that even knowing that temperature rating, nobody can tell whether or not they, or in fact any glove, would work for you. To do that, we would need to know how hot the thing you are carrying is, how much time you will hold it, and the R (or thermal resistance) value of the glove (which nobody reports.) 

So you might have to just try some gloves, and if they don’t work, return them. Barring that, I would try making some mittens out of quilted cotton and canvas or leather for the shell. They don’t have to be beautiful. Make sure you don’t use any polyester, not even polyester thread (you can use cotton, or Kevlar thread if you want to get fancy). Or metal staples, etc. Or I might make a secure carrying tray out of wood. That way, you only need gloves to move the pot in and out of the tray, and you wouldn’t have to worry about hustling to the kitchen before you burn your hands. Properly made, it could give you larger and more secure carry handles. The tray should have high sides so the pot can’t slide out and you don’t accidentally touch anything that might melt or burn (like your forearms). Ideally it should fit closely around the pot. It might almost look like a square bucket. 

I use welding gloves from Lowe’s, whatever brand they have. So long as I don’t let the glove linger very long, I’ve not been burned yet, using them to move burning logs, fish out objects from coals, reposition fireplace or grill grates, or move Dutch ovens around. They will burn if you neglect them too long, but for the fifteen bucks I tend to pay every third year, they are a bargain to me.

These are nice, and are nomex/kevlar, so they resist heat pretty well, and the silicone lines give you decent grip.  They are knit, which lets heat escape quickly, and let your hands breathe, but if you were to spill hot water or grease on them, or put your hand in escaping steam, it will get through quickly and burn you, so you still have to be careful with that.

EDIT: more thoroughly re-read the original question, and realized you\'ve already tried these, so never mind...