I did they same, had a tank full of lionfish that assisted in the culling process.
You just have to decide the level of acceptability, ("grading") and yes scoop out th efish via a net.
The reason you want to place these fish in a container is so the less obvious ones get seen from the sides-makes grading easier.
If you are like most of us, you really don't want to pass on any visible deformities, and Please i don't want to see any caudal-less fish (called half-moon) on the market. :^( ticked me off last time i was at the LFS they had half/moon parrot cichilds-crazy and frustrating