Seems his refusal is rooted by fear of failure.
I agree wet wipes are easier.
Understand that the action is actually quite complex.
(my 9yr old has Down syndrome and is still not able to do it well)
You could practice the action together with hand over hand help
Praise for any attempt or even asking for help
Realise this won’t be for ever, in some years you look back and smile

Flushable wipes might help until he gets more skilled at the task in hand.

I have this issue with my son but its due to laziness. I find if I don’t go running in to wipe his bottom he eventually does it himself. No 6 year old wants to wait around sitting on the toilet!

i have this issue too. She does wipe, but not properly. love the idea of the wet wipes at home…will make life a lot easier…thanks for the tip! sorry im not much help for original poster

You’re not alone. I was still wiping my youngest sons bottom when he was 6 too. I used a reward chart to get him started, lots of encouragement whenever he did give it a go and I would check for him to make sure he’d done a good job – usually required me to finish the job, but still plenty of encouragement for doing his best. As soon as he was doing a decent job, I backed off on the checking and let him judge for himself if it was clean enough. He’s 8 now and I can’t remember when I last had to help him with it.

While at home let him use wipes for a few months, its so much easier to clean their own butt by themselves with them… But explain to him that when out at school etc its important for him to use paper and wash his hands properly afterwards.. Is there any chance he might be constipated? i always thought the same with my daughter she was always staining her pants… but it ended up she was constipated and need a long term soultion… If constant staining of undies is involved go see a doctor for advise….

Continually tell him he smells, make dry retching sounds when he’s been to the toilet to emphasise that he smells. Tell him people won’t like him if he doesn’t wipe his bum cos he smells. And buy some wet wipes, he might find these easier to use