If you're confused about the order of events, here's how I did it:
*Opened DAYZ
*Joined a server
*Went into the game, crouched.
*PRessed 'G' to open inventory
*Opened cheat engine
*Did all the changes on the engine
*Got back into the game (inventory still opened) and shift+p
*Got my stuff..
Note: The one time I tried to shift+P with my inventory closed, I got an error. So, make sure your inventory is open before you shift+p, or even make changes to CE. (Just to be sure)