I used to render lard that way until I used the microwave and found it was faster, cleaner and didn't stink up the house!
Just put the fat and meat in a deep microwave-proof glass container with a lid. I have a deep Corning Ware ceramic 3 quart bowl with a glass lid that is perfect. They're available at WalMart and you'll find a million other uses for it.
Set the power on HIGH and in minutes you'll have clear hot fat with bits of crispy leftovers. You can throw those away or chop them up and mix in once they cool.
Birds love peanut butter and the really cheap stuff in big plastic jars (keep the empty for nuts, candy, etc.) is great to mix in. I also buy bulk oats, corn meal, and flour to mix in as well as crushed breakfast ceral. The mix-ins can be anything in the back of the pantry that can be crushed or broken up in a blender or food processor.
I too use to render fat, especially beef fat (tallow) because I use to make homemade soap.
There is a big difference in fat when it comes to soap. Tallow makes hard soap like wax, olive oil makes tiny bubbles, lard makes slimy soap, coconut or palm makes great big fluffly bubbles (but all alone it will dry out the skin) I use to mix my fats to make very nice soap. I used them all except the lard.
Anyway you are right in your article, I would ask the butcher at a meat producer to save me back pieces of beef fat. I have not done this now for a decade and it was 10 cents a pound back then too. Glad inflation has not affected fat.
I put mine in a great big canner with no water or anything. I put the setting on my extra stove (that was outside in the garage) on very low and let it go all day long. It just kind of melted down. It at first did not smell very good but by the end of the day, oh mine, it was wonderful! It also confussed my family into thinking I actually had a good dinner cooking. They were always disappointed if dinner turned out to be salmon patties instead of beef burgers. It was kind of cruel.