The best thing to do is not to wash the grapes after you buy them, because the fermentation of the native brewing system relies on the wild yeast microbial fermentation attached to the surface of the grapes, and you can't wash them by hand, brush "poor" wash, and you can't use detergents, potassium permanganate, and other disinfectant drugs. To maximize microbial survival.
Industrially, grapes are not washed, and many large wine companies have their own vineyards where the use of chemical fertilizers and pesticides is strictly prohibited. It is difficult to guarantee that pesticides will not be used on marketed grapes, but as far as I know, fruit growers generally avoid spraying pesticides directly on the grapes, because it will form spots on the skin and shorten the freshness of the grapes. (If you're really not sure, you can wash the whole bunch with water.)
The grapes are then crushed as much as possible with clean hands and canned with the skins and seeds. Industrially, the grapes are crushed in a crusher. In France, the traditional method is to hire pretty young girls to climb into the barrels and crush the grapes with their feet. In the industry, it is also used to extract the juice from the grapes in a press and to ferment only the juice.