Slower scroll

How can I make scroll slower on whole site? It means, for example, that to scroll 100 px i need to do 2 scroll steps, but I want this number to be bigger. I found a way to do it by animating all layers going down with the scroll, but after that i can’t normally animate separate elements. Maybe there is code to implement to do it?

I once implemented the scrollmagic js:

This worked pretty good but needs some customcode knowledge to get it to work in readymag though.
Here is an example of how fluid a scroll can be using this js: