If you can see the gas breaking out of solution in the lines when it's just sitting, then it's either still overcarbed, or the lines are significantly warmer than the beer in the keg. My guess is that it's still overcarbed, since it takes a lot of venting to degas a keg that's even just a little overcarbed.
FWIW there is a very quick way to degas the keg, but it could remove more carbonation than you want. Put your gas line on a liquid QD, and push gas through the liquid diptube at a couple psi while holding the pressure relief valve open. The turbulence caused by the bubbles will knock a lot of the CO2 out of solution. Doing this for 30 seconds at a time 4-5 times will be enough to degas even a severely overcarbed keg.