First thing to do is download Cheat Engine.
Then u have to join a public session and kick all players, so u will be alone in a public session. (There are tools on this forum that allow u to do this)
Now, open Cheat Engine and put GTAV.exe on it and enable speedhack at 40 approximatelly and go to your bunker if you arent there. And now you just need to wait.
Thats all. I unlocked all in less than 5 minutes.