I had just under 9L in an oak barrel, so very little yeast in suspension (1275) and very little CO2.
I had 1/3 packet of M79, rehydrated, with about 7-8g/L of dextrose solution which should be about 2.5volCO2. It has worked wonders before, e.g. using wine yeast for cider or S-04 for beer.
It has only been 10 days, but there was only the slightest, minute hiss, the beer is dead flat and there is a nice slurry on the bottom of each bottle. So I wondered if it flocs really well and relies on continued suspension to multiply (i.e. the Burton Union system), so in my bottle conditioning situation where there is still, enclosed wort it has just flocced out without doing any multiplication/chewing.
Another bottle may be different, and obviously another week or two could help... but using this method normally gets me nicely carbonated in 1-2 weeks.