As noted in the self sufficiency forum, tomorrow is hen murder day. One aspect of old hens is that because they don't put a lot energy in making eggs anymore they become rather obese.
Most of the meat will become dog food. However dogs can't tolerate the quantity fat an old hen often contains. So, I'll skin the birds (after plucking), and trim out as much fat as possible. The skin will be made into chips and the rest of the fat also rendered with the skin. When i culled a hen a couple years ago, that single bird yielded 1.5 pints of rendered oil. That was exceptional, but half to a full pint is typical.
Super easy. I find glass casserole dishes work great. Put skin and some fat in the dish, sprinkle with salt to taste, and bake at 325F until the skin is crispy. I dont add water. I'll usually flip the skin when the top side is getting close to done. Pour fat into Mason jars once you're sure it's fully dried out. It usually is when the skin chips are crispy, but an extra 20 minutes in the oven after removing the skin chips won't hurt it.
Some people add onion towards the end, but I have never bothered.
SWMBO doesn't like it for some reason, but it's my personal favorite oil for cooking eggs, potatoes, browning meat for a braise, etc. My boys prefer it too.
At room temp it's a cloudy thin jelly consistency. In the fridge it will solidify but is easy to spoon out. The freezer will make it quite hard, and also allow it to stay good a very, very long time. Even in just the fridge I've kept the same jar for many months. I do salt the skin and fat before rendering. And I make sure all moisture is driven off.