As daCoda pointed out, you leverage your instructions by picking things that are repeated.
Not all hours of the day are created equal. Some tasks have to be done at a certain time. Writing instructions doesn't require you to be in a certain place at a certain time. Maybe you could write instructions on drop shipping a package while waiting for an appointment, but it's not convenient to bring all the packing materials and drive to the post office. Writing the instructions may not take as much concentration. I could sit in a noisy area and explain what to do, but may not be able to focus enough to do the actual work.
Some people do things better Even if they don't, learn how to delegate. The old saying, "If you want something done right, do it yourself." does not fit all people and tasks. And what is "right"? There is a point when you have to accept good enough. Too often people confuse "my way" with absolute correctness. Select tasks you don't do as well and probably shouldn't be giving specific instructions. This saves time and improves the quality.
Eventually, you'll get better at hiring and working with other people, so you don't have to always give lengthy instructions. Everyone will start to understand what is expected along with the level of quality you want. Using a virtual assistant should be part of a larger evolution into delegating and leveraging your time.