I hear you -- they're a pain
I've been working on my adjustable spring plates on and off for months... But, today I got it nailed. After doing it several times to get it right, it seems easy now. I re-indexed both sides in about 4 hours. Consider it a right of passage...
Know that you WILL do it (many times...).
With the spring plate tool, there is no worries. Just work on one side at a time. With the stiff-*** adjustable spring plates, I had to remove the IRS pivot point bolt and washers to allow the trailing arm to move outboard. This may help you too. Then loosen the torsion bar cover and remove the spring plate bolts. Now jack the trailing arm up as far as you can go so it is almost over the top of the spring plate. Now with the spring plate on the stop, use the tool to just barely lift the s/p off the stop. Then wedge a pickle fork between the spring plate and the shock tower to bend the spring plate outboard past the edge of the stop. Now loosen the tool to lower the spring plate past the edge of the stop. Stop and measure the distance from the bottom of the spring plate to the top ledge of the stop so you know where it was before your adjustment. Take off the tool. Use a claw hammer to gradually pry the spring plate away from the shock tower. You want it to come loose from the splines slowly so you can feel the splines while you rotate the spring plate up one notch (to lower car). You may need to grab the torsion bar while you pull the spring plate out. Rotating the s/p is the hard part... I have 944 torsion bars and lowering the rear about 2.75" puts the bottom of the spring plate close to the middle of the side of the spring plate stop on my 70 bug.
Once indexed, push the plate against the stop, then start the torsion bar cover bolts and snug. Attach the tool and lift the s/p up onto the stop. Torque the torsion bar cover bolts tight. Lower the trailing arm and start the spring plate bolts, but leave loose. Replace the trailing arm fitted bolt and washers, tighten (90 ft-lb) and dimple colar to prevent loosening. Adjust toe and camber, then tighten torqued down spring plate bolts (80 ft-lb).
Lower car, bounce on bumper to settle. Measure torsion bar bottom to ground on both sides. Repeat until correct.......
Remember, rotating the inner spline up and outer spline down (or vise versa) at the same time splits the difference of rotating the inner or outer up one. You may need to do this to fine tune the ride height.
With the torsion bar free of torsion, but still engaged in the spring plate/frame, measure the distance from the bottom of the spring plate to the spring plate stop and adjust both sides so they are equal (level side-to-side ride height). Then adjust both sides relative to your first measurements -- rear of spring plate goes up, car goes down... If you can slip the spring plate over the spring plate stop without the tool, you're in the weeds (too low in my book)...
Enjoy when you finish, endure in the mean time.
Bill