There are a bunch of ways to fast carb, but each comes with the risk of over carbonating. Getting excess co2 out of the beer sucks an can take a few days on its own.
If I need something to be ready next day, I jack the pressure way up, 50 or so, and shake 75 times. I disconnect it and let it sit cold. Next day I slowly bleed the pressure and hookup at serving temp. It is usually a bit under, but after another day or two it is spot on.
If I need something in a few days, I set the pressure to 30 and give a few shakes every so often. After 2 days I dial the pressure back to serving pressure. Again, it is usually a little under carbed, but I am ok with that.