I like to do as much as possible at one time, because it's a messy job. Cleaning up once after 10lbs is much better than cleaning up 10x after 1lb batches! Also, it will render faster and more cleanly if you can run it all through a meat grinder first.I usually buy my tallow. But, I’ve been given a bunch of fat for free! How much do you render at once? Wet or dry render?
I start with dry rendering in my large electric turkey roaster pan out on the back patio. I strain off all the rendered fat into some smaller containers, preferably bowls that will easily release the chunk of tallow without having to dig into it. I let it all cool down to room temp, and then put it in the fridge.
After it has solidified, I take the chunk from the bowl, turn it over, and scrape off the bottom where the gunk has settled. I save all the bottom-scrapings to wet render separately with my used cooking fats that also have more gunk in them. That allows for faster and easier wet rendering of all the cleaner chunks together, to remove the last impurities and smell.