I've found that it happens when the concrete is covered, like a carport. It has a certain look, like a sheen. Also, could be the mix or the temperature when it cured (too cold).
I swirled one up once and developed an eye for it real quick. Do a test spot on a corner with a wand and find out how much it can take. Then.....yep, do it with a wand. I had one recently where I wanded under the carport and used the s.c. on the rest, have done that several times actually and they come out good.
As for getting the swirl marks out, you can even them up with a wand (square instead of circular) other than that maybe someone else has an idea. Maybe a good time to sell them a coating! I know it s**ks, Good luck.
Dan Stapleton
352-343-2811