I do a similar thing - that is, slip the spring over the cable, but to compress the spring, I use a miniature pry bar (looks like a "Wonderbar" nail-puller) about 6" long. The pry bar has a notched end, for nail-pulling purposes - but here you'll use the notch to push one side of the end of the spring.
With the car well-supported on jackstands, reach around the strut to grab the inboard side of the spring with the "front" hand, pulling the end of the spring forward (towards front of car). At the same time, push on the outboard side of the spring using the heel of your hand against the "L"shaped end of the prybar, and catching the end of the spring in the notch on the prybar's straight end. You're using the prybar as a pusher. It kind of looks as if you're giving the strut a hug.
Between the one hand pulling the spring on one side, and the other hand pushing on the other side of the end of the spring (using the little prybar), you should be able to manage to get the spring hooked onto the E-brake lever on the caliper. Once that's accomplished, you can slip the cable end into its slot of the E-brake lever, either by hand or using slip-joint pliers
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