Once you are in Zombie Blood mode you will have limited time to search for the possible perk bottle dig site locations. The good thing about the dig site is that it does not change until the perk bottle is dug up, however finding that location can be difficult and quiet time consuming. The best advice is to search multiple dig sites at one time and rule them out for that particular perk bottle drop, However for each subsequent perk bottle dig the spawns reset so its completely random and you will have to try all locations again.

Another thing to note is that you need to buy your first 4 perks normally, minus Double Tap but including Quick revive. Once you have your 4 Perks you can now dig the different locations.

Next once you have dug up the 4 extra Perks slots and filled each up with a different Perk ( Minus Double Tap) continue to he rewards chest at Generator 1 or 6 and claim your reward for spending 30,000 points. Claiming this reward will give you your 9th Perk which is Double Tap and you now have all 9 perks available on Origins.

The Dig Site Locations include:
Near Generator 5 and the Soul collecting Chest.
Near Generator 5 in a Foot Print near the excavation site.
On the tank track heading away from Generator 5 but towards Generator 2.
Near Generator 2 at the end of the Dead end trench.
Behind the tank station at Generator 2.
Under the Remington outside the Spawn.
On the pathway to Generator 2 just outside the spawn room door.
In the Fire Crazy Place Tunnel.
Near the B23R near the Spawn.
Beside Generator 3 near the window.
On the tank path back towards Generator 3 heading away from Generator 4
Near the excavation site and soul collecting chest in a robot footprint.
Beside Generator 4 and Juggernog.
On the tank track heading towards generator 4 from generator 6.
Right next to Generator 6 and the Remington.
On the tank track heading from Generator 6 back towards generator 5.