If you have a competent staff, you can train your employees to perform just about any job in your company. But the key is training. You can just expect your employees to "pick things up" as they go. If you want an efficient business, you need efficient employees, and it's your job to give them the tools to succeed. Follow the "tell, show, do, review, do again/follow-up" method. There are many different learning styles that people have, and this method trains to them all.
Tell. Explain to your employee what it is the he needs to do. This is your time to clearly state the expectation for future behavior. Speak slowly and clearly. Repeat the essential points that need to be understood and why they are important. An important note, though, keep yourself from talking down to the employee, and allow open dialogue. Train from your own experience, and if you have background info or a story to tell about what you're teaching, now is the time. People remember stories better than bullet points.
Show. Demonstrate to the employee exactly how you want the job to be done and go into details about why you want it done that way. If you are cutting a tomato, train her how to cut it to the exact size you want it to be, and explain why it needs to be that size (taste, appearance, etc.).
Do. Allow the employee to do the task on his own, but guide him through the process. If you see him struggling with a certain technique or mechanic of the process, demonstrate it to him again.
Review. Go over with the employee everything that she has learned. If she is still struggling, go back to Step 2 (and review your own training technique!). Ask her questions to ensure retention, and answer any questions she may have. Have the trainee "teach" the task to you to check for complete understanding.
Do again/Follow-up. This is the ongoing training that continues until the employee has mastered the task. Be constructive, and use your own knowledge/experience when offering feedback. Most importantly, keep your cool if the trainee doesn't pick up on the task as fast as you would have liked.
Be patient. Be present (devote the time to the trainee). Be clear (explain exactly what you want so there isn't confusion later on).