Place the spring flat on a hard level surface.
Tie the string around the spring, place the string through the middle of the spring, to the outside. The string will keep the spring stable and in place while rewinding.
Start winding by hand. Once the spring becomes wound tightly, clamp down with the needle-nose vise grips.
Untie the string from the spring. Place the spring into the recoil. Tip the spring into the casing, hold in place with one hand while pressing down and unhinge the vise grip with the other. Install the recoil housing.