I was practicing the technique of Jacques Pépin for peeling garlic when I remembered what I had seen on the internet. Some people on the internet shake garlic in a bowl covered with a plate or they shake it in a jar to remove the skin from the garlic cloves. This seemed magical, but the technique works well. Jacques Pépin lightly slaps a garlic clove with a chef’s knife . This technique works well.
Here is how I am currently cutting onions. For dicing the onion, I do not believe that cutting the onion horizontally is necessary. The onion is constructed in layers the fall apart if the pieces are squeezed (compressed) with a hand. If the pieces are not squeezed, then controlling the size by cutting the onions horizontally may be desirable.
Here is a pepper. I used the part of the blade of the knife nearest to my hand to scrape the seeds from the flesh of the pepper to remove them from the peppers.