I kegged a Hefe about 4 days ago and I took a taste before bottling and it was way over carbonated. Is there any way to get some of this carbonation out?
If you pour it and all you get is foam from the tap. It's over carbed. When you pour you should get about as much head as you would a commercial beer on tap.
Also sometimes it can taste a little acidic due to the high amounts of carbonic acid.
It's dependent on the style, because Stouts will typically be a lot less carbonated than a Wheat beer. That being said, if it tastes too fizzy, then it's over carbonated.
You can also push the carb out of solution by putting the corny keg diptube into the gas side. Open the top. The CO2 pushing through the bottom of the soluton will degass the solution in about a minute and a half at about 8-12 PSI. There's a YouTube video on this method, if you can search it.
pressure will equilize over time. if you have ++pressure in the head space of the keg, the beer will take up that pressure. if you have --pressure in the headspace, gas will leave the beer.
shaking just does it faster. you can also put a spunding valve set to the pressure you want and leave it for a week.
shaking and releving pressure after yep! make the CO2 come out of solution.
thats the quickest way, the slower way is just releving the pressure every few hours or once a day