There are a few methods to completely rid the tank of these nudis.
What I did was to dilute some lugol's iodide in tank water and dip each infected piece for 3 minutes, then repeat once more in 2 days. However, the iodine dips do stress out the already weak SPS and is more risky.
A less damaging method is to scout the tank every night for a couple weeks and use airline tubing to siphon out any nudis you find.
Six-line, four-line, and yellow-coris wrasse are also reported to eat these pesky nudis, but don't count on them completely destroying the entire nudi population.