The trick is to get them square with each other. To do this you need to intall the back 2 with handle out the front and the front 2 with handle out the back (middle doesn't matter). The insures that the tool is straight and the bearings will end up straight.
Before I got my own tool, when a machine shop would install the bearings, the cam would always be snug when turning. If you do yourself and take your time the cam will spin easy.