This all depends on where and when
If at a social event.
1: Cough loudly, or attract attention some other way; if at a formal dinner gently tap your glass
2: Give a short speech extoling the virtues of behaving in a natural manner rather than conforming to social norms.
3: If you talk loudly enough the sound of this speech will mask the sound of your fart.
On Public transport, or in shops
1: Fart as normal, do not adjust buttocks in any noticeable way
2: Regardless of sound or odour or absence of either, give a disapproving look at the person sitting nearest you.
As for social situations above, though you may need to check your workplace regulations to ensure that short speeches are allowed. If speeches are not allowed behave as for public transport.
Friends and Family events.
Proceed as normal, ask for marks out of ten for odour, sound and any special effects.
Finally, in churches, theatres, cinema or operas, silent or silent but deadlys must be ignored, if noise is anticipated time it to match a loud part of the service, play, film or opera. Either that or creak seat at the same time.