The key is compressing the pillow before you fart, then unloading your weight as it comes out. This causes the pillow to ingest all the surrounding air. Some shillows can hold the stench for 15 minutes in perfect conditions, giving lots of opportunity for a sneak attack.
>WHAP!< throw pillow hits Steve in face thrown by Jim
"Ugh, bastard, you startled me!" Says Steve, then suddenly "OH CRAP, what's that smell?!? (dry heaving) I can taste it! Was that a shillow??"
"Hmm.. that's odd.. I don't smell anything over here. I don't know what you're talking about." Jim plays it off legit.