Kids seem to pick some of the most gross issues to express their need for power and control over. As I raised my daughter, I became exasperated over some of them that she chose.
At the time, I thought that the solution was teaching, teaching, teaching, and more teaching.... consequences rarely happened because I was trying to be such a thorough teacher and give her the benefit of the doubt. As a result with some of her self initiated power struggles, I ended up just struggling through teaching her how to do the task -forever- never being able to let go and allow for natural consequence. She still seems to be unable to get her brain in gear to do laundry, make her own peanut butter and jelly sandwhiches, and completely clean her room. She's 16 now. For a long time now, though, I realized that by her NEVER being successful on her own, she was manipulating me by punishing me with her stupidity (on purpose). I know it sounds mean, but what I mean by stupidity is that she would stupify her own brain and absolutely refuse to think for her self and accomplish the task, thus putting the burden on me to struggle with her through it, take my time to keep her on task, and just be a burden in a way that she KNEW was irritating to me. It was all about power and control on her part. And believe me, whenever I did LET GO - absolutely nothing was accomplished - until I kicked in and helped her. She went unfed, unbathed, uncleaned... and just didn't give a damn herself.
My husband's take on it was "Good, if she stinks and she can't find clean clothes in the mess, the boys won't like her." So, I let it go.... I let her stink up her body, room, life and go hungry for her peanut butter and jelly snacks.
It took years but, she's finally come around a little bit. She's still a much grosser person than I. I personally feel uncomfortable with a dirty butt... and whatever... but I had to come to terms that if it just doesn't bother HER -well, so be it... that's how she want's to live.
So, for my kid, she did choose the cleanliness issue as her favorite issue for power and control. She's had a hard time overcoming it and only rarely "gets it" that she's only hurting herself by doing it. All I can do is hope that someday she'll give it up.
So, that's all the experience I have to offer. It would be that this uncleanly issue may not be due to your teaching, or lack there of... or even the option of baby wipes. It just might be the one thing that he loves to do to punish you... the stinky butt. He may have chosen that to be his source of power and control. But, he's not the first kid to use that technique. Someday, he'll understand that he's only hurting himself (and other's noses with the smell) when he doesn't wipe his bottom. ---It may be a while.