I find that minimizing shoulder contact helps a lot, but it's the consistency that counts. My trick is to only allow the bottom tip of the butt to touch my shoulder, rather than the entire surface. This gives me a very easy to repeat pressure.
Apply shoulder pressure with the hand holding the forearm NOT the trigger hand.
Posting 5 links about the same thing is a bit much, yes?
What works for me is a "light grip"; without getting too pedantic about it. That is because every springer and pellet combination may work slightly better if you shift the forend support point (front to back) relative to the balance point. Likewise; you may want to try different positions and loads applied at the shoulder. Even the "best hand" to apply such force is not a given. It is your job to find out what your airgun likes, and to practice that until it requires no conscious thought to achieve it: