Dissolve 220g of 5-12-26 into 32 oz water.
Dissolve 148g of Calcium Nitrate into 32 oz of water.
Now you have two stock solutions. 10ml per gallon of each will give you an EC of about 1.2 (600ppm on .5 scale).
If you want to include Epsom salt for extra mag, dissolve 72.6g of epsom salt into 32 oz of water. 10ml per gallon works out to about 1.2g/gal.
With the above solutions, the 3-2-1 method is as simple as adding 10ml of each solution per gallon of water. You can adjust the concentration by either making stronger stock solutions, or just using more than 10ml/gal. The important thing is the 1 to 0.67 ratio of 5-12-26 and CalNit.