If you don't want to mess with the paint methods, there are lots of other options. Depending on how big of screen you want, you could go with Parkland Durotherm Lite panels. They are a corrugated PVC material that is 4' x 8' x 5/16" thick. One side is smooth/flat/matte white and works great for a screen. Many on AVS use this method and trim or incorporate a masking border to get the desired size. It can be found at Menards in the paneling aisle, or may be available at Lowes or Home Depot. There are other options like Black Out cloth that can be found at JoAnn's Fabrics, or just Ultra Pure White Flat exterior paint works good as well, on un textured walls...
M80s-VP180-QS8s-EP600-2xEP350 Denon3808 Outlaw7700
(M22-OWM22-VP100)-all in storage