I just finished quilting a 30" square wallhanging using Mountain Mist fusible batting, I had no problems at all with puckers or wrinkles...this time. I did tape one third of the backing snug on my ironing board, smoothed the batting on top of it and then added the top and pressed, once the part on the ironing board was smooth and fused, I moved to the 2nd third, taped and repeated. Once it was all fused, I add pin the outer corners to keep it from shifting. Worked well.
And as another poster suggested, I do let my batting "relax" before sandwiching, I pull out of the baf and spread it on the table/bed the night before I sandwich it.
Hope this helps! It does take patience, lol.