Cape stun> double tap Space. It stuns them and leaves them vulnerable to an attack from above, which is the double Space where B Man vaults in the air and lands on top of them. Alternatively, and this is better IMO, you can save up your chained combos for these tougher foes and use the Disarm and Destroy Special Combo.
D&D is better because B Man breaks the shield so no other thugs can use it. It's even better if you have the perk unlocked where you can trigger a special combo with fewer chained strikes. Nothing quite like being low on health then coming through with a well timed D&D when you need it most. It's confidence inspiring when used well.
When he destroys the riot shield he grabs it and whacks them with it before he breaks it. Normally one wouldn't think of a riot shield as a weapon, but since they can bash you with it, technically it can be used as one. That doesn't mean he'll rape the armored clowns of their steel plating though. Wouldn't THAT be strange. :lol:
Forgot to say that one of the better places to experiment with D&D is in the Funhouse Brawl fight. All you need do is line yourself up so the one armed guy is between you and a guy with shield, stun baton, etc, punch him until your combo builds high enough, then tap the D&D key. B Man will then automatically jump to an armed opponent directly in front of him and D&D.