I suggest doing this in Ranger Mission 3 or 4. Since there are no lasers to reflect back onto enemies, you're going to have to use the mechs' laser that they shoot at you. Switch to your Refractor and run up to a mech. Look around in first person for other enemies and as the mech fires at you, you'll reflect it back towards the enemy. Once the regular enemies are dead, reflect it back at the mech. Repeat this until the skill point unlocks.
Keep in mind that this is not cumulative and has to be done in one go.