I prefer to use bullet connectors between motor and ESC. Lot's of folks use solder on these joints for a very good reason. One loose connection on a multirotor motor circuit can spell disaster. In addition to the possibility of a loose connection, it is often the case that the heat shrink insulation can leave a small gap between the two parts of the bullet. I want all my electrons to stay where they belong : /
So here is a solution to both issues:
Break out the manual 3D printer(hot glue gun)
Cut out a piece of silicone sheet to use as an ad-hoc mold
Apply a small bead of the glue and use the silicon to shape a thin film evenly around the joint
Peels off cleanly when you need to break the connection.