I have done a D9P with 3 fabrics several times. What I did was use fabric 1 for the 4 outside corner squares, fabric 2 for the 4 outside center squares and fabric 3 for the center square. When I made it I used WOF strip sets (3 strips per set) and crosscut them. So using this method I made strip sets with fabrics 1-2-1 and 2-3-2 and another of 1-2-1, crosscut and sewed the e crosscut pieces together to make the 9 patch block which is then cut into 4 quarters. Hope this makes sense!