I had several water leaks in the ceiling and I had to replace a section of the drywall in the ceiling. The drywall is 1/2 inch thick. I installed it, its flush to the existing drywall. But now I realized on the existing drywall theres about 3/16 of an inch of compound/primer/paint, I dont know what it is. Any suggestions on how to get the new dry wall to be flush with the existing drywall?