I have to 100% agree. The better prepared you are going in, the better things go even when it all gets FUBAR'd in mid process. Table reads, Rehearsals, Lighting tests, SFX Tests are all important. With that said, when shooting a funding trailer it's a great opportunity to do all that before you go into actual production. As Budget goes Estimate High then Spend Low. Invariably unexpected costs creep in at the most inopportune times. IF you have any money left over after Post, there's seed money for Festivals.