We recently purchased a drill auger bit to speed up planting and can’t recommend it enough. Here’s the one we purchased, which included bonus transplanting tools that have also worked well for potting up plants:

There’s a lot of similar products available in various sizes, but we went with this one as it was just smaller than the 2″ holes in our landscape fabric (similar to Floret’s technique shared here) and just bigger than the size of plants grown in our Neversink trays.

We run our drill in reverse as we found it to actually dig too well in forward. This gives us more control over the depth and prevents the direct from refilling the hole.