JRDavis is right on track about using low heat. You just want to heat the chunks, not fry them. As you start heating the fat, it starts to become somewhat opaque, looking wet. Let me back up a second ... fat is made up of millions of globules ...micro-balloons if you will. As fat is heated the fat in the micro-balloon is turned to liquid and the heat weakens the outer membrane permitting the liquid fat to escape the broken membrane when pressure is put on the chunk of fat. I use a small spatula with slits in the spatula, and a thin steel skillet. As I press on the heated fat, liquid fat is released into the pan, and I pour that off into a jar. I keep up the pressing and pouring until I get a good amount in a jar. A baby food jar is excellent. After the fat cools, it becomes white, like thin lard. I'll put the jar with the lid on tight into a pan of very warm water, or over the heater vent and remelt it until all becomes liquid again. It is set aside and as it cools, the fat separates. the oil floats on top of the thicker fat below. I siphon that off with an eye dropper and put the liquid, watery fat (oil) in small bottles I can close with a cork. That watery fat stays watery, like oil, and that is what I use for patch lube mostly. The other thicker lard-like fat can be used also. Mixed with a bit of beeswax, you can make it the consistency of natural lube 1000. Or you can use it as a water proofer for boots, moccasins, etc.
Bear fat is amazing stuff as patch lube, and bears oil after rendered doesn't go rancid readily. I've had some in bottles for 2 years, and it's as good as the day I made it.
I hope this helps answer your question.
Ohio Rusty