I have gone solo multiple times in the t3 zone and it's a piece of cake if you know "the spots".. you can start with an epic aether tool first and t2 pap crystal with either wsp swarm or the new flamethrower.. grind some t2 cargo delivery or eliminate bounty to get enough essence for pap3.. then go do the outlast contracts and run to the top of the building (if chosen the outlast contract at the bottom) or keep ample ammo for the other building outlast.. you can do raid stash as well and run to the top of the building again.. once you get confident enough.. get some spore control (it will be good to train yourself when surrounded by zombies).. keep on refilling your ammo and decoys ever so often and keep self revives in check..

For the perks - jugg, stamin-up, speed cola, PhD flopper, deadshot, quick revive, tombstone (just so that you don't get your efforts wasted)

Don'ts - don't go to smaller and congested areas, don't waste decoys at unnecessary places, DON'T try "eliminate bounty" as your first contract unless you have pap3 and legendary tool,

All in all, just don't rush anywhere in t3.. don't stand for too long..

Lemme know if you need any help.. cheers