I've done this thrice. Once for a Pink Floyd tribute show, and once over a theatrical B&W movie. In the first case we used manual sync, the 321-Click method, which can work very well with practice. In the second case I used SMPTE time code recorded on a audio track. Its not widely used, but there are many features in the Pangolin commercial software for doing this, and Pangolin sells a SMPTE reader module in hardware.
Do I have any guidelines for Laser total power vs Lumens, no.. But I will tell you to get a very small beam diameter in whatever you buy if your "rotoscoping" over film/video. Rotoscoping is the trade name for tracing a animation by hand into laser graphics, by placing a cartoon cell or video frame in the background of your laser editor and tracing the outline by hand. Most commercial laser show software has autrotrace of some form, but the best work is still done by hand.
Dr.Lava the creator of LSX has his own module you can buy as well, that autotraces video.
Steve
Qui habet Christos, habet Vitam!
I should have rented the space under my name for advertising.
When I still could have...