I make my own suet mix. I start out with beef suet but I think you could use pork too. I ask for the scraps the butchers throw away. But it is cheap anyway. I then cut it into small pieces and render it over low heat on the stove. Use a big pan and watch it so it doesn't get too hot. You will see the fat begin to seperate from the bits and raise to the top. It takes awhile so be patient. After it is all seperated I either scoop out the bits on the bottom or strain them out. I set these on a platter and let cool since the birds love these bits. Then while it is hot I add peanut butter. I like to use natural PB as the other has added sugar. How much yoo put in is up to you. You can then put this into forms after all the pb is melted into the fat or you can then add other things. I add shelled sunflower seeds, cornmeal or even the packaged bird seed. If you are using plastic forms (I reuse the plastic trays from boughten suet) make sure the fat mixture is cool or it will melt the plastic. Also it helps if you add stuff to let it cool enough that the seeds stay mixed up and doesn't settle to the bottom. Be careful because grease fires are so very dangerous!!
Lynda