My son had a hard time with getting used to pooping on the potty, he was peeing by the time he was 3.5 but didnt master poop until just over 4. He was afraid of sitting on the potty (not sure why). Pee was ok bc he could stand. Anyhow, to get him to poop we would have him sit and give him an activity to do so he would get distracted and not hold it in. I also bribed him! LOL! Told him if he pooped on the potty I'd buy him the big firetruck at Walmart that he had been eyeing! It worked, we were at my sisters one day, sat him down on the potty, and he played with a couple of toys and then he did it! We went to Walmart immediately and he proceeded to telleveryone he passed, "I'm getting my fire truck because I pooped on the potty!" it was funny.

As for wiping, he is grossed out by poop, even now (hes almost 7) if its a particularly yucky one, he will call for me and try to get me to wipe for him (to which I refuse, I mean hes almost 7!). So he does wipe but usually goes through a lot of toilet paper bc he doesnt want to get the poop on his hands. I also make sure I have thoes wet wipes for older kids (not the baby wipes) so he can get himself as clean as possible. Maybe that's whats up with your non-wiper, he's grossed out by poop! Even his own!