Stephen
I grind the fat through a meat grinder using the course blade so it releases more of the fat.
I use a 5 gallon stock pot, that cake is laying on the one I use and I put enough water in the pot so it covers the fat and put it on a hotplate outside, you don't want that smell cooking it on your Wife's range in the Kitchen LOL.
That batch of yellow fat took me several days adding water several times to cook down. The first time I let it simmer for about 8 hours and let it set and cool over night. The next morning I lifted the cake out of the water and scraped the jell off the bottom and set it aside and cooked the mix left in the pot again and that gave me about another inch after it cooled.
Scraping the cake off again I dumped the water and cracklins in the pot out in the fence row. It make good Coyote bait

This time I put the cakes back in a pot of water and let it simmer under a little higher heat and let the water just about cook out and added more and at the end of the day I just let it cool and the next morning I scrape off the jell again and I have a old freezer that don't work anymore and I use it for storage for things like this.
This batch I had to render a little longer because of the yellow fat. Normally with white fat it would take 8-10 hours and it would be as hard as a candle.
It's a little time consuming but the effort is worth it.
Kurt