I was told one story, I don’t know if it’s true. One shooter had a bad habit practicing with live rounds at home. First shot was at TV, second at the wall and third shot at the wall resulted a divorce… So, always practice with dummy rounds, it is better to put all live rounds in a safe or in another room, so you have no chance mixing live and dummy rounds.
I don’t like plastic dummy rounds, they are expensive and they have light weight which makes them inappropriate for dry fire trainings.
Shotgun dummy rounds should be of the same weight and size as the live rounds. This way, you will have proper skills during dry fire trainings.
There are two best variants to get such dummy rounds for your shotgun. First is to make them yourself. If you have friends which reload shotgun shell you can ask them to make such dummy rounds for you. You just don’t add live primer and gun powder. That way you will have dummy round which has the same weight and size as live rounds.