It is fairly easy to do. To render suet, I buy 5 pounds of suet from the grocery store, I grind it up in a meat grinder attachment to my mixer. I put in in a huge stainless steel soup pot covered in water. I let this come to a rolling boil and watch that I don't let too much water evaporate. I add more water if needed. This could take 30 minutes to an hour before all the suet it melted. I let it cool down on the stove and then strain it through a wire mesh colander, the gristle and bits will stay in the colander, the liquid I put into a big round plastic cake cover and pop it into the fridge. Leave it overnight. What you get is the white fat layer on the top and the water with yucky stuff on the bottom. I take the white fat off (it's very hard now) and put it aside and dump the bottom stuff down the drain, mixing it with lots of hot water and some dawn dish washing liquid. I can then rerender it if I don't think it's pure enough although most times it is. It's very smooth and white and much nicer looking than the suet. I then can use it or put it in the freezer until later.
I had to do a presentation on soap making for boy scouts and this was part of the presentation, to show how they would have taken animal fats in years past and make soap the old fashioned way.
Some notes...you can cut the suet into pieces but grinding is much better and faster, doesn't melt nearly as nicely when just cut into chunks and you have to boil a long, long time and sometimes mash it into hot water with a potato masher to get the fat to release.
Do in a small amount first, that pot of hot fat/water is awfully heavy if you have a couple gallons of it and if your container to go in the fridge is flimsy, it will spill and be a mess.
It really is worth the time, not difficult to do but it does smell a little while boiling.
Good Luck.
