Tordon is available at most farm supply stores - Rural King, TSC, Agri Supply, etc. It is about $15 for approximately a quart size bottle that has a squirt top on it. You literally cut the tree or bush and put a ring of Tordon around the outside of the fresh cut and forget about it. As Sonny 580 said Cut/Chem/and Cover and you are done. The keys are that you need to apply it very quickly after cutting - <15 minutes or so - and then let soak in for a couple of days before you cover.
There are other brush killers out there, I just got started with Tordon and it works for me so I have not changed.