Typically when bottle conditioning a homebrew it takes at least 2 weeks or more to properly carbonate the beer, however if you need to carbonate the beer faster, we have a useful trick that will reduce the carbonation time to just 6 days.
All you have to do is gently rouse the yeast and invert each bottle once per day for the first 5 days after bottling. After chilling the beer for a few hours on the 6th day it will be fully carbonated, this will work even for high ABV stouts that would otherwise take 3 weeks to carbonate.
Basically this just wakes up the yeast which is resting on the bottom of the bottle and increases their surface area, allowing the yeast to work more efficiently.
See the video below for a demonstration. Happy homebrewing.