You can secure most molding directly to drywall with a crown molding nailer and liquid nails. Just drive two nails at 45 degrees in an "X" pattern every 12" or so. They will hold the molding against the wall till the glue dries.
JVC RS-540, Sony UBP-X800, Onkyo TX-RZ730 (7.2.4), Onkyo M-5010, Elite Screens 100" 16:9 (Spandex AT DIY)
DIYSG 1099 LCR, Polk TSX-150C (DIY) Atmos, Yamaha NS333 Surround & Surround Back
Triple HS-24 mkiii 11cuft sealed, Behringer NU-12000, Crown XLS-2502, MINIDSP 2X4