The classic use of speedbrake is Intruder's scenario: capturing GS from on high. Set a controlled ROD (~1500ft) and wait for GS capture. Of course, you keep configuring as per normal - if speed reduction doesn't occur, pull out the speedbrakes. Selecting Level Change/FLCH/Open Desc is asking for very high, unknown rates of descent
Totally disagree.
VS is for low rate of descent in TMA during CDAs..
If you need to increase your rate of descent,(ie above glide slope)use LvL chg and adjust speed to get your desired rate of descent.
Now you have speed protection and you dont have to destroy that energy with your
speedbrakes.