double valve spring ques

This may serve as a bump rather than actual help, but are my thoughts:

By inner and outter springs, I assume you mean intake and exhaust. Now, I do know that when you change valve springs w/ the heads on the car, you need one of the fittings to screw into your spark plug hole to blow air in the cyclinder w/ a compressor and hold the valves up...otherwise you'll drop a valve into the cyclinder, which probably isn't what you want to do.

All I can say is the autozone valve spring compressor didn't work as easily as I hoped and I ended up just taking mine to the machine shop (heads already off the car) to get my valve seals changed. I had trouble with the keepers not wanting to move, I believe was the issue.

it's not impossible, far from it in my experience. i was loaned a valve spring compressor from autozone and it worked well on both springs.

the spring tool should push down the spring retainer, which will compress both inner and outter springs at the same time, then pull the keepers with needle nose pliers, sometimes a little tap from a hammer helps break the keepers free.