Basics
There are only two real choices in this build, and it's designed to utilize all three of his strengths (AE damage, shields, and disruption) without overspecializing, while minimizing weaknesses. The biggest loss is in single target damage. His CC will also end up a bit weaker, so if you need more snares or roots, you can swap talents around to accommodate that. Those are the choices I mentioned.

I mention pubs specifically because he excels at working with a partner...but pubs often have their own ideas and leave you soloing a lane or holding objectives on your own. His root-kick, snare ability and pure tankyness makes other builds amazing when working with other players, but when I found myself alone and other players not co-operating, he was utterly inept solo. This is the best jack-of-all-trades build I've found, and compensates for chen's weaknesses and potentially having derpy teammates. Think of this as a solo queue build to utilize to be good at everything, great at nothing, and able to work on your own as needed.

With this build you can solo waves and towers a lot easier, and support teamfights effectively. You can harass a few people at a time and hold objectives. Your weakness is finishing off enemy heroes and doing single target damage. This is not your role anyway.

Talent Choices

Tier 1
Consuming flame : The logic here is that deadly strike is more suited for single target, and while full keg is fantastic CC, we're focusing on AE damage so that we have a way to clear minions/towers and do some damage in teamfights.

Tier 2
Chug : Bottomless mug isn't really worthwhile since chugging your brew is something you should be doing constantly. Deep breath's 25% radius isn't really needed since you can hit a full wave of minions regardless, and the size of your keg splash is only going to amplify damage on a small arc of fire anyway.

Tier 3
Ring of fire or pressure point : Pressure point is an amazing ability if people work with you. If they're not, I tend to operate on the assumption that snares and roots still won't provide the opportunity to finish people off solo. Ring of fire will increase your AE DPS substantially.

Tier 4
Storm, earth, and fire provides both an emergency escape, a second health bar, and amazing disruption potential in teamfights.

Tier 5
Choice #2. Enough to share is useful since you're going to be chugging a lot of brew no matter what. This gives a fair bit to your allies and stacks well with combat stance. The alternative choice is a touch of honey if your pubbies are being good and you want more CC.

Tier 6
You lose the respectable single target boost of combination attack in exchange for longer-lasting shields. I feel like at this stage in the game, your shields usually fade before enemies knock them down. This increases your survivability by a truckload in exchange for a damage loss. This is another choice you can make depending on how the game is rolling.

Tier 7
Chen is already pretty hard to kill; this lets him take more risks in late game and come back instantly.

Gameplay
Pretty much start your pub game hoping that you have competent players. Depending on how well they work together, use another build! If reality kicks in and they're not working together, afking at random, and leaving lanes free, then spec according to this guide. In a perfect world you really wouldn't need much AE damage and would be focusing more on CC and disruption, but I've found myself soloing lanes and working objectives alone pretty frequently. Having that AE damage is more useful than CC or disruption in those conditions (which pub games tend to facilitate).