What is the discomfort level of Dermasound?

I use Retin-A micro 0.04% nightly for acne. Would this be helpful at all for post inflammatory hyperpigmentation (red) I have on the front of my neck from a recent cystic breakout? Definitely concerned if it hurts and there is a special on 1 or 3 treatments. Wondering which, if any, to purchase.

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