You prune the same way as if the tree was full size. Open up the canopy to allow for airflow and sunlight. Getting to know your trees and the growth cycle is the most important. Main pruning is done after the harvest. Some trees i only prune once a year especially if had fruit, but if the tree doesn't flower or if only one section flowers i might prune it down so branches don't get too long or it will bend to the ground. You'll have 3 years of pruning before the trees start producing so you will get a lot of practice and everything will become more clear..

I do regular soil/tissue analyses so i can see what it needs. I primarily foliar feed because my soil is really alkaline. I start ferts after harvest and pruning. I use 4-10-40 once maybe twice a year. I also add ferts when applying fungicide or pesticides. I use miller microplex, i use a calcium+boron mix, kelp extract.

8 feet in row 10 feet between rows

All trees are different. Some are more vigorous, some have thick unbendable limbs, some have lots of shoots. Some trees take more work to train on a trellis, but most trees will work