Don't EVER knee them in the chest!!! We humans aren't very coordinated and have kneed dogs in the chest that broke ribs.... and there are incidences where someone broke their dog's rib in such a manner that it pierced the dog's heart for near-instant death. Not a risk I'm willing to take.

Its all about attention. Why do they jump? Because its 100% effective in getting attention. We all bend down to pet them to keep them from jumping up. Practice practice, practice him learning that jumping up get NO attention. No words, no touch, no visual intereaction. NOTHING. Ignore them until all 4 paws are on the floor - either by standing politely, sitting, or laying down. They usually figure out pretty fast that when all 4 paws are on the floor that people approach them.

Get him into a sit stay before you open the door to let guests in. Work on making a reliable sit stay and he'll remain in it if he's been taught he HAS to remain in the sit stay. Or work on down stay if he's more apt to remain in a down stay. Work on tricks that reinforce sit stay or down stay so that he comes to think of it as a nice thing to do.