How to make drawers close softly?
You can either replace the slides with a soft closing model, or you could possibly shoe horn in a damper piston like this one made by Blum.



They work in the same way as the ones in your link (those are made to attach to a hinge) but it can be recessed into a block or, in theory, drilled into a drawer side. The process would be to attach the piston in whatever fashion works with the pin pointed to the back of the cabinet. When you close the drawer the weight and momentum compresses the piston before it contacts the end of the slides travel, effectively softening the landing. You may have to apply a block on the back of the cabinet to give the piston a place to contact at the correct depth relative to the position of the drawer when it's fully closed.