Sometimes I experience an itchy anus and I came to the conclusions that on occassions, after a BM, there's an acidic residue, which with normal wiping & cleansing, still remains within the anus.
My solution, is to wrap my finger within a wet wipe and insert just the tip of my finger & wet wipe into the anus.
I repeat this, re-wrapping my finger within a clean area of the wet wipe and inserting until the wet comes out looking clean; I only have to do this twice, maybe three times just after a BM and only when the itching occurs.
Although, this sounds rather messy, uncomfortable and somewhat unpleasant, I can assure you it isn't and it's preferable to the discomfort of an itchy anus throught out the day.
On occassion, I also apply a small amount of ilex paste.
If you've not already tried ilex to alleviate your butt burn; I suggest you give it a try, in my opinion, it's by far the best solution.
The makers of ilex provide free sample sachets prior to purchase, although I managed to aquire a free tube from them.
In the UK, ilex Paste is also available on NHS prescription.