Recently I bought six 12ga 'snap caps', made by "A-Zoom". I've been using them to practice acquiring/handling/cycling my Mossberg 500 from its storage position at home. And man, these things are really terrific. They allow me to handle the gun around the house, just like I would in a real situation. And I can 'fire' and cycle the rack without blowing my house apart, LOL. Of course, when pulling the trigger (even loaded with just a snap cap) I have the gun pointed in a safe direction. But still, I can easily (and for zero dollars) practice handling this firearm in my house.
If you can't get to the range, or just want to brush up on how it might feel to actually operate your shottie inside your house (instead of only at the range), then by all means, grab some of these snap caps and have at it. These are same size and weight as 2 3/4" shells. They are available in assorted sizes. Very handy items! I can't believe I waited this long to buy some.