Well first off, pooping your diapers / pants is an acquired taste. I went through my childhood being attracted to diapers and started wearing them for fun when I was about 13, but for peeing only. I tried pooping them once when I was about 20 and couldn't stand the smell. Tried it again when I was about 26, same thing. Doing it felt great but I couldn't stand the after-effects nor the cleanup.
Then when I was about 35, for some reason, I decided to try it again and actually liked it. Probably because I was under lots of stress at the time and on that particular day I REALLY wanted to escape into my "baby" world. So, after putting on my diapers and wearing them until they were good and wet, I realized that I had to poop, felt this really naughty feeling, stuck my thumb in my mouth, and stood there and babyishly loaded my diapers.
This time, when I smelled the smell, it was still pretty horrible--but it now just drove home the point of what a big bad diaper wearing toddler I was and that feeling made me extremely excited.
After that it was "Oh that was bad I'm not going to do that anymore" then a few weeks later, out of nowhere, I had this insatiable desire to do it again. Over time I got over the smell and now associate that with all of my other diaper wearing fun.
It's interesting to note, though, that context is everything. If I'm wearing diapers and baby clothes and let go and poop my diapers, I love it. If I'm not in "baby mode" and go to the restroom and take a dump, I still can't stand the smell as much as I always couldn't.
As for the lingering smell afterward, if you clean up in the shower it will go away in an hour or two as you air out. The content of your poop has a lot to do with it. If I know I'm going to have a day at home by myself when I can poop my diapers and wear them for a while, for a day or two prior, I'll mostly eat salads and vegetables, very little meat, no fish, etc. Also I take Metamucil with my meals. This has the effect of increasing the volume of the load, but also, it moves it through your digestive system faster and that seems to cause the smell to not be as bad.