First you must complete all of the missions to unlock Survival Mode.

Start the game on survival.

Spawn an Arty.

Upgrade your Arty (to run fast)
Click on 'I am ready'

Run away from the enemies for as long as possible in order to wait for the Anti-Personnel Turret (APT) to become available for deploying. (don't try to attack anything, just run)

You may get bitten a few times, just laugh when this happens.

As soon as the APT is available, deploy it and hang around it while it kills the enemies.

Once the APT runs out of life, run away and deploy the Anti-Vehicle Turret.

Repeat this method until there are less than 10 enemies left.
Hint: You CAN use grunt or gunner instead of Arty at the beginning by modifying the above strategy.

When the glowing red enemy direction indicators are no longer flashing, you know that the only enemies left now are the ones visible.

When you have less than 10 enemies, let them kill you, lol. They will just stay at your corpse and feed on it until you spawn another Arty.
Press c for fast mode to get blood faster. Don't kill anything until you're ready.

When you get enough blood, spawn 15 Artys then spawn Doc, quickly kill the remaining enemies with your APT and the 'I am ready' button appears, heal your units, place them around everything you laid down earlier when you were waiting for man blood.
I would have stopped playing this a long time ago, but knowing this has really made this a fun game and I love trying all kinds of strategies to try and beat my wave 38 record on easy mode.
I hope this will bring more fun for the players and if the devs see this I hope they don't fix it. But if they do, I hope they make a sandbox mode in place.

Help me Obi-wan...you're my only hope.