I really didn't plan to start with a screen and am building my HT right now. To start, I was going to just project on a sheetrock wall and if I can't stand it, then buy a screen. Is a screen an absolute necessity or can I do this without one? If I can do it without one, how should I prep the wall? Should I use flat, semi-gloss, high gloss and how about white vs the ultra white paints? Thanks in advance.