I found a good warm bath and actuation of the blades under water helped enormously, and then lubricating the pivots once dry made a massive difference
Short fingernails are strong, longer ones get broken. I keep one thumbnail quite short and use it to hook the nail nicks. I play guitar so the nails on my left hand are all quite short. (If you are right-handed) the left thumbnail is not really involved in guitar playing - can be whatever length you want. I keep it very short and use it to open SAKs. Saves the longer, right-hand nails.
I find it's mostly about the angles. A lot of people instinctively try to lift the tool with their nail stuck into the nick at 90º. Instead try a digging motion, so you end up with the nail pointing up into the nick toward the top edge as much as possible. That way you have the force more in-line with your nail instead of working parallel against it. Then again, my own S667 springs feel soft as knicker elastic, so maybe it is a strength factor...
Agreed! But watch out -- you can end up with a drawerful if you pursue this rabbit hole too far.