That is extremely bad advice. Over pressurizing, shaking, and then letting it sit at excessive pressure for several days is one of the most effective ways to over carbonate a keg. Over carbonation is just one thing that can cause excessive foam. It is likely at least part of your problem.
I recommend strongly against agitating the keg when using higher pressures than required to achieve your desired carb level at the current temperature of the beer. If you want to agitate the keg to speed up carbonation, you should use the pressure (from a pressure/temperature/carbonation chart) that corresponds to the desired carb level at the current temperature of the beer. With this method it is not possible to over carbonate the beer. When you're done agitating, put the keg in the kegerator/keezer and set the chart derived pressure for your target carb level and refrigerator temperature. It will still need to sit for many hours to settle down after the agitation.
The easiest, safest way to carbonate is the "set and forget" method. Just pressurize the keg to the chart derived pressure required for your desired carb level at your refrigerator temperature. It takes two to three weeks to reach full carbonation with this method. Many brewers are too impatient to use this method, but you cannot over carb your beer this way.
Another way to do accelerated carbonation is to set the pressure to 30 psi for 36 hours,
with no keg agitation, and then turn the pressure down to the chart value. This is the method I use. You can still over carbonate if you let the keg sit too long at 30 psi, but if you are careful about the time, the method is controllable.
Brew on