1. Opening the game- Tap the Dead Trigger 2 icon on your mobile device to open up the game.
2. Expensive way- You can spend a lot of gold coins, which are the premium currency. Or you can unlock some for free with the next steps.
3. Minibosses- There are mini bosses in the game by the names of Kamikaze, Vomitron, and Scienfist. Killing these mini bosses will net you some blueprints.
4. Strategy- Play the Attack stages on Easy mode. Doing this will give you an opportunity to kill more than one mini boss in a stage. Playing in Defense mode gives you a finite amount of time.