What do you think about this method to punish/teach a dog?

From one of the books I read the writer suggest a method to keep your dog from eating food from outside. There are some common issue in this country where some outsiders(especially dog haters/silly people) throw poisonous food to your yard for your dog. And he suggest this the method:
“Dip a food/meat/or else in chili water,call some of your friend(that your dog never meet before/strangers) and ask them to throw this food to your dog from outside your house,let the dog to eat the spicy food,repeat the process each day until it refuses to eat a food that is threw by strangers/outsiders.”

And the method how to make your dog refuse food from strangers by their hands:

“Dip a food/meat/or else in chili water and give it to your dog with both hands,repeat this process each day and your dog will refuse food from strangers if they try to feed your dog with one hand”

I taught my aunt about these method and she said it works,even though I didn’t try these method myself while I was having my own dogs(since they’re indoor).
Any thought about these two methods?