D.W.
Adele,
I had this problem with my youngest son. We went straight to underware. When he had an accident, I would be the one cleaning out his underware. When I asked for advice, I had an aunt to tell me that I did not need to be the one cleaning out his underware. She suggested that I explain to him that it was his mess and he would have to clean it up. He had to get the poop out of his underware by using the water in the toilet. I would get him clean and make him think that I was going to take care of the mess. Before he could leave the bathroom I told him that he had to clean out his poopy pants. It only took 2 or 3 times of him having to handle those poopy pants before he figured out that Mom was not giving in and the best way to not have to touch the poopy pants was for them to not get poopy to begin with. He cried, screamed, and pitched a fit the first time (which expect yours will do the same). Keep your cool, but stand firm. I know it sounds mean, but it is effective. Plus, my son learned that I was not going to clean up after any mess that he made (BONUS!!!)
Whatever you decide, I wish you luck!
D. W