Changing Drain Planet to Drain Ships

I'm trying to change Drain Planet to a ability where the ship would channel and slowly drain away hull of the target then transfer the hull back to the ship.  At first I change "DoDamagetoPlanet" to "DoDamage", but that only deals damage to myself.  Changing it to "DoDamageToTarget" still doesn't help, plus apparently the DamageAffectType also becomes invalid.

So I tried applying a buff to the target to do the damage and restore the hull of the caster when it is channeling it.  However the buff is only a overtimeaction and the buff stays there the whole duration, rather then stopping when the channel is interrupted.  I could also make it apply a 1 sec buff every second to do the damage, but that seems inefficient and unstable.

Am I missing?  It seems this should be quite easy to do, and I feel like I'm thinking too complicated than it should be? Thanks.