Following the method in "Every able body", you can probably knock out this achievement and that one at the same time. This is best obtained during a bonus wave. Simply ONLY summon swordsmith allies and farmer allies, otherwise this achievement will not unlock. You ARE allowed to use your powers as you hover through the lane as a "ghost" unit, just don't summon any allies other than those two. If you go through the 50 waves without getting this, simply load back up one of the bonus waves, which appear every 5th wave, and focus on getting it.