Well, did we really help the the starter of this thread with pictures of tools that will not answer the question ?
First remove the fuel tank. My approach on a tight shell is toothpicks. Next I use an exacto blade to slim the toothpicks down to a thin, flat edge and then insert two of them one each side of the loco so that the shell is pried open enough to no longer be bound by the retaining "bumps". Then a firm grip on the shell and the bottom of the frame usually does the trick.
Good luck
eja