Creating Ground Vias

There are two ways.

1. as you said already you can place a bunch of vias and set them as ground seeds.

2. create your ground fill and then place the vias (no need to set the seeds)

The advantage of 2 is that it does not create a gap around the vias with traces connecting it. These gaps are required when soldering to a pin connected to the ground fill because the ground fill would pull away the heat too quickly to get a good solder joint. But with vias in the ground fill we do not need this heat break and we would actually rather have it transfer heat really well.

The disadvantage of 2 is that you need to delete the vias and replace them every time you want to re-generate ground fill because if they are in place already it will create the gap. I usually save the file right before placing the vias, generate gerbers and then revert the file back to before the vias were placed.