It's true- I'll waft them up to my face, or fart on something then smell that. I've noticed a difference between smelling farts off my fingers and farting into a towel and smelling that. I prefer the towel. Sometimes, right before I take a shower, I'll wipe my ass with a towel or my underwear to smell my butt-perfume. I frequently pull the covers over my own head when I fart between the sheets. Oh, and I love the smell and frequency of my hangover farts. I love leaving my room for a few minutes and coming back to smell my still-lingering farts hanging in the air. To me its kind of like climing out of the swimming pool, getting in the hot tub for a few minutes, then going back into the pool. If I want to fart without making a lot of noise I'll reach into my pants and hold my buttcheeks apart with my fingers so the gas can leave my asshole unobstructed. it actually makes a very audible "pssssssssssssss" sound. Like if someone was in earshot but they couldn't see me, they would probably be wondering if i was farting with my fingers in my ass.
Sometimes if I'm in public I'll find "discreet" ways to indulge my fart-sniffing penchance. For example I'll try to pass gas as quietly as possible, then discreetly fan my thighs open and closed so the gas is wafted up to my face.