I have suffered the same issue on and off for several years. It comes and goes and has caused so much suffering. Have you tried to use EFT- just tapping, no words, when you are in the middle of having a blush attack?
Can you ask a relative or friend to stare at you so you start blushing and then just tap on all your points? I would advise to tap slowly and gently with a breath in between points, I know at times when we're stressed and tap EFT we can sometimes hit so hard and fast that it makes the anxiety worse. Also make sure you drink water so you're hydrated when you tap.
I've never tried to tap EFT when in the middle of blushing, only when I'm relaxed thinking about blushing and it didn't help. Maybe if you tapped when in the middle of blushing it could release the stress and bring about a positive change to how your body reacts.
You might also want to look into PEP, it's like EFT:
How to Do Positive Energy Psychology - PEP - (Positive EFT)
https://www.youtube.com/watch?v=PtIzYwAlMn0
PEP for feeling peaceful well-being: Positive EFT for anxiety, stress, worry, and more
https://www.youtube.com/watch?v=tB8OaxwUD2Q
Hope it helps your situation and you find some relief :)