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One method that some brewers attempt is adding a small pitch of ''Brettanomyces'' to a clean beer at bottling time. This can be done either in the bottling bucket/tank, or added to each bottle individually. If adding ''Brettanomyces'' to each bottle individually, a 1 mL dosage of ''Brettanomyces'' from a starter should be enough since pitching rate seems to have little impact on the beer <ref>[[Brettanomyces_secondary_fermentation_experiment]]</ref>. Some brewers believe that adding the ''Brettanomyces'' at bottling time results in a more complex beer. It is speculated that the extra stress of pressure within the bottles helps to create this complexity.
One challenge with this approach is that it is difficult to predict how much ''Brettanomyces'' will further attenuate the beer once in the bottle. Over-carbonation and bottle bombs can easily be an issue with this method if the brewer is not careful. Each degree Plato adds ~2 volumes of CO2 <ref>[http://braukaiser.com/wiki/index.php/Accurately_Calculating_Sugar_Additions_for_Carbonation#Remaining_or_Residual_Extract "Accurately Calculating Sugar Additions for Carbonation." Kai Troester. Braukaiser.com. Retrieved 08/07/2016.]</ref>. Daniel Addey-Jibb, co-owner and brewer at Le Castor near Montreal, Quebec advises that the approach that his brewery takes is to ferment their saison wort down to 1°P. Once at 1°P , the beer is cold crashed, fined, and then bottled with ''Brettanomyces''. The beer is then stored at room temperature for three months to condition naturally in the bottle. During bottling conditioning, their ''Brettanomyces'' culture takes the beer down below 0°P, and their desired level of carbonation is reached. This process took Addey-Jibb's team dozens of trials to perfect using their specific wort recipe, saison yeast, and ''Brettanomyces'' strain. Different species or strains of ''Brettanomyces'' might ferment differently, and different wort compositions might also ferment differently. For example, Addey-Jibb's saison is mashed with malted barley, wheat, and rye at a low temperature so there are not many higher chain sugars, allowing the beer to dry out quickly <ref>[http://www.thebrewingnetwork.com/session-le-castor/ Addey-Jibb, Daniel. Interview on the Brewing Network's Session podcast. 10/04/2016.]</ref>. Other wort compositions that include higher chain sugars from specialty malts and/or higher mashing temperatures might ferment much slower, and thus knowing what the final gravity will be once ''Brettanomyces'' is added is difficult to know without running trials on that specific fermentation profile. It is recommended to use Belgian beer bottles of sparkling wine bottles that can withstand higher pressures than regular beer bottles just in case over-carbonation becomes an issue.
A "forced fermentation test" might help to determine the final gravity of a given ''Brettanomyces'' strain or blend of strains. Use the same wort composition as the beer in question, and pitch a large cell count of ''Brettanomyces''. Use a stirplate if possible, and an airlock to keep oxygen out (some ''Brettanomyces'' strains can attenuate further when fermented aerobically and thus will not give an accurate final gravity reading when fermented aerobically). Keep the temperature around 80-85°F for a month or two, and then measure the gravity. Each gravity point gives produces about 0.5 volumes of CO2. Adjust the priming sugar for the rest of the batch accordingly. Use bottles that are rated for higher pressures, such as Belgian bottles or sparkling wine bottles <ref>[https://www.facebook.com/groups/MilkTheFunk/permalink/1536542119707330/?comment_id=1537256646302544&reply_comment_id=1537384512956424&comment_tracking=%7B%22tn%22%3A%22R0%22%7D Conversation with Adi Hastings on MTF regarding forced fermentation tests with ''Brettanomyces''. 1/2/2017.]</ref>.