Does your FCTM say you should or have to level off to extend flaps? If not, what is wrong with extending them in a descent with minimal deceleration, just as you retract them in a climb?
The issue of using the flaps "as speedbrakes" is separate, though related. If ATC-mandated higher-than-desired speed causes late deceleration, flaps plus speedbrakes (or flaps plus gear in the case of airplanes like the 747 Classic where flpas + speedbrakes are prohibited) may be required at higher than "flap maneuvering speed" in order to decelerate, descend, and configure in time.
Granted, with perfect planning and execution you will not have to "use flaps as speedbrakes." However, we fly in a very dynamic environment...