If I understand correctly it has a built in regulator that stops the c02 at the "appropriate" time. They say you need to shake the container when done to infuse the c02 into the liquid quickly. I've never used a keg setup so don't really know the process and it very well might be the better option. I was just researching options. I was also wondering...I have a handheld C02 pump for my bike, would there be a way to use that to carb a poured beer into a plastic bottle. I don't know how I would regulate it though and how to not let the pressure escape when I remove the pump?
Right, it's definitely got a regulator mechanism of some sort, but it doesn't have an
adjustable regulator. If you can tweak the pressure output, you can carbonate to any degree that you want.
The CO2 pump for your bike uses 16-gram cartridges, I assume? If so, you would need a way of attaching a valve to a soda lid somehow. I've seen people do it, for example here:
http://www.examiner.com/article/build-your-own-carbonator-cap
If you are going to be doing this often, though, it's worth investing in a CO2 tank. Those cartridges don't last very long, and they'll get expensive quickly. You can get a CO2 tank and regulator for something in the ~$150 range (often cheaper used), and that would let you put a ball lock valve (the "carbonator cap":
http://www.amazon.com/dp/B0064OKADS/?tag=skimlinks_replacement-20) onto most plastic soda bottles.
If you go that route, you can carb up very quickly. Between my first post in the thread and this one, I carbonated four liters of fizzy ginger soda and am drinking it right now. Takes a minute of shaking or so, but it's pretty simple and foolproof.
FWIW, I don't love doing beer this way, but it works. I tend to have pretty poor head retention with insta-carbed beer, possibly because of the shaking.