This Seeking Tech guide will show you how to get the Firestarter trophy and achievement in Mouse P.I. for Hire.
To do so, you need to “Blast 20 enemies in a single playthrough by shooting at explosive barrels.”
Follow the video and text guides below:
You can farm the kills early in the game during The Vanishing Act level, when you first learn about kicking explosive barrels. Instead of kicking, shoot at the two enemies ahead to lure them to the barrel and then shoot the barrel.
Do not move forward too far, or you will trigger the auto-save.
Instead, reload your game from the previous save to put you near where you were previously with the barrel. Rinse and repeat this process until the Firestarter unlocks.