Growing Container Potatoes

Should you fill a 10 gal grow bag 1/2 full then place ? Number of seed Potatoes cover and fill until container is full? Or, just place seed potatoes in the 1/2 filled container then fill with soil? How often & what is a good fertilizer. I plan to start with a mixture of organic potting soil, worm castings, perlite, peat moss and compost! Help