The official tool may be more trouble than it's worth. It's single biggest advantage is that one person can do it.The problem is that most of these tools use a screw thread to create the required pressure. This is a very poor use of standard screw threads and most novice users will gall the threads on the first chain rendering the tool unusable.
The way we do this at the shop is to assemble the masterlink, then approach both sides of the chain with long heavy steel rods. One rod acting as the anvil, the other as a "drift". Then a right smart rap on the drift upsets both poles of the rivet link. No muss, no fuss. The job is finished in seconds, but it does require 2 people.
The first time this was described to me I thought it crude and inelegant, but when you see how fast the work goes you'll find a permanent place on the peg board for that chain tool.