I'll add my two-cents here. I've never used a tool, other than perhaps a pencil when seeds germinated really erratically. What we do here is to soak the pot in room temperature or a bit warmer water- then let it fall on the table, or just pull the soil into tow or more parts, which will come apart pretty easily. Then, we just pull the outiside seedlings away from the mass, always holding the plant by it's leaves (which, if broken, unlike a root, will always be replaced). We then dangle the roots into a small indentation (probably made with a finger), gently push the soil around the plant, and tighten, making sure that the crown is above the soil line. Then, we gently water the plant in.
By the way, we are pricking out of small (2 1/2" or 4" community pots) and replanting into either standard 1020 flats or 4 inch pots.
Rika Willow Pond Nursery http://www.willowpondnursery.com