If you wish to use mild and vitamin based suppository that can calm and lubricate the area you may try "Key-E Suppositories" based on coconut oil, palm oil end vitamin E. There are suppositories that contain cortisone and need to be prescribed but they can make area even more sensitive and thinner if used for longer than 2 weeks. I never personally had radiation induced protections, but I had some "issues" and found those Vit E suppositories useful. Hope they help.
PS: I also think that your description of the sensation is very good. Irritation can also cause nerve endings to act up and make that "buzzing" feeling. Some doctors are just very limited in anything else but one thing that they do , unfortunately.