Unfortunately, I’ve never seen potholders from Dollar Tree.
Polyester has so many varieties that it’ll require some testing on your part. Luckily, there is another user on the forum who makes great tutorials with settings with all forms of polyester and other fabrics. I’ve linked a few down here, since each post has a different type of polyester along with her settings for each.
I would choose one with low power and high speed to test first, since polyester is man-made and apt to melt. Good luck.