Never tried it, but normally you do not want any sheen or hot spotting. Actually the formula has gone through many changes since I used to hang out at the DIY forum for screens on AVS. I spent lots of time testing and trying various samples and formula's that took lots of time. There may be some new changes I'm not aware of.
Some have been happy with just Behr Silverscreen, which does not have as many different ingrediants.
Matte White (flat) screens have been around the industry for ever, and are the norm. Some people like high power screens, but I think you start to lose contrast. Others like to use Contrast enhancing screens, however, you lose color vibrance.
The Z4 has great contrast that rivals some DLPs that are out there now. Also, colors are dead on with the Z4. Most likely you would be happy with just a matte white screen.
Another option, if you have a home improvement store around is to look for Parkland Durotherm Lite panels. I bought them at Menards before, they come in a 4' x 8' x 5/16" thick light weight panel found standing up in the paneling aisle. One side is smooth flat white and works great for a screen. Just hang it and enjoy. You can paint your back wall black or build a black border to help with perceived blacks. In my opinion, a border or painted back wall is a must. It really improves the picture quality. This material can also be trimed to accomodate a 16:9 screen.
Here is my Dazian matte white 2.35 cinemascope screen.
