For DM-run characters using NAD attacks,
- Add +20 to the attack bonus to determine the DC
- Roll damage for the attack and set aside
- Have each target roll 1d20 + Target Defense
- If the target result is less than the modified attack bonus the attack hits; Otherwise it misses.
- Resolve any "Effect" text for all targets.
For player-run characters, attack as normal.
This basically just shifts the math for the attack so players can roll the dice. If you find it easier, you can have the players subtract 10 from their rolls and compare it to attack's bonus directly instead. Short and simple! I'm going to give it a try in my campaign and see how it feels -- if anyone gets a chance to use it, I'd be curious what they think!