Weigh the meat in grams. Divide the total weight by 1000, then multiply each ingredient by that number, except the water (see notes). For example, if the combined weight of the meat and back fat is 3650 g, you need to multiply the ingredients specified above by 3.65.
Cut the meat into 2" pieces, mix with salt and Cure #1. Place in a container, cover, and refrigerate for 24-48 hours.
Remove the meat from the fridge and separate the lean pieces from the fatty ones. You will need to do some trimming at this point - the fat will go into the fatier meat pile. Cut the lean meat into 3/4" - 1" pieces. You should have roughly 50% lean and 50% fatty pieces.
Grind the fattier pieces through a 3/16″ (4.5 mm) plate.
Place the meat, seasonings (pementon, garlic, and oregano), and water in a bowl of a stand mixer fitted with a paddle attachment. Mix for 3-4 minutes. This will mix the meat and tenderize the meat chunks, which will help with stuffing. If you don't have a stand mixer, grind the lean pieces through a stuffing plate or 3/8" (10 mm) - 1/2" (12 mm) plate, or cut them about 1/2" big, then mix by hand or in a meat mixer.
Stuff into 28-32 mm hog casings at 16" lengths and tie into rings.
Dry for about 60 minutes in the smoker at about 110F - 130F without smoke.
Smoke at around 130F - 140F for 2-4 hours, with blue smoke, until the casings develop the desired color.
Gradually increase the temperature in the smoker to about 195F, until the internal temperature of the sausage reaches 154F - 158F.
Alternatively, and more reliably, poach the sausages in 167F - 176F water for 25 - 30 minutes or until the internal temperature is at least 154F. Poaching is a much quicker and more effective method.
Place in icy water for about 5 minutes, then let cool down further at room temperature.
Store in a refrigerator for up to a month. Freeze for more extended storage.
Notes
I usually add another 60 ml at 3000 g, then another 60 ml at 9000 g, etc. But also keep an eye on the consistency. If the meat is stiff, add more water.