...what does it mean by enough to balance the drag?
This refers to your level off altitude, after drift-down. At high altitude, you don't have enough thrust operating at single engine to maintain your level. The thrust generated by the remaining engine operating at maximum continuous thrust will increase as the aircraft descends and eventually it will equal the airframe drag. This process is applicable when you wish to maintain altitude in order to miss high ground.
Once you have levelled off, you have to decide what you want to do next. If terrain clearance allows, you now have to consider where you wish to go. If it you choose somewhere close by, you might even be too high! But if flying a long distance, an appropriate speed has to be chosen and if fuel is a problem, the speed to pick will the one that gives the best ground distance per kilo. Almost certainly that speed will entail flying at an airspeed higher airspeed than Vmd meaning that your aircraft will again descend as you accelerate to this speed. Again, the descent will be arrested as the thrust equals the drag resulting from flying at this new, higher airspeed. Assuming you have compliant ATC, it might be worth trying to "block off" some sky ahead of you, say from 1,000' beneath to 3-4,000' above you level and allow the aircraft to slowly climb as it gets lighter. It will also give a margin should temperature fluctuations and turbulence change your performance.
PM