Cloak:  hold triangle, press square, O, O, square, release triangle  hold X, 
press triangle, triangle, release X

Speed:  hold up, press triangle, triangle, triangle, release up  hold down, 
press X, square, O, release down

In game code, yes, you might waste some ammo.

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In the, ooh mental block... what are those blue things with
big claws called again?  Throgs?  Anyway, the Throg breeding
facility has a secret entrance to a level called the "Lost
City."  It is in the lower right hand area of the map--you need
to break open about 3 or 4 secret doors there before you can
reach the exit.  The Lost City is full of insect-monster larvae
and the Throg-Viscerian genetic brain mutations.

- Zen