"Randy White, the Dallas Cowboys Hall of Famer, was one of the first defensive linemen to use karate training, a discipline that has become more popular in football today. Hand fighting is a skill that all defensive linemen must learn. It can be done without pads on, making it ideal for spring workouts, especially at the high school level, where players may not be allowed to wear pads.

In this drill, two players stand across from each other at no more than arm's length. The "offensive" player repeatedly attempts to strike the defender's chest with his hands. The defensive player must react quickly to keep his opponent's hands away. At no time during the drill should either player move his feet. Beginners should focus on knocking away the hands, but experienced players can practice more complicated techniques such as arm-overs and rips."

http://www.stack.com/a/defensive-linemen-drills

What are pass rush techniques? Bull rush, speed rush, grabs, swim, spin, rip, etc. In linemen you look for footwork and hand techniques. Better question is how would it not help them?