Just like all the other DLC leader achievements, the Sgt. Johnson ones can be obtained pretty much the same easy way.If you want to do this the fastest method for just the 15 Healer Beacons, then do this:
Setup a Skirmish Match with these settings:
Game Type: Strongholds
Fog of War: Off
Power recharge speed: 200%
Any other helpful skulls can be turned on, put the AI on easy.
Don't forget to pick Johnson as your leader!
As soon as the match starts, select your Armory and train Johnson. As soon as he's out, select Johnson, press
on the ground near him, then wait 30 seconds to do it again. Repeat 15 times! You might want to grab all the empty strongholds otherwise the AI "might" rush you and be annoying.Otherwise, if you want to get all 3 Sgt. Johnson DLC achievements somewhat at the same time: