Molds are shipped ready-to-cast.
I do not use a release, and don't recommend it.
Back in the day, when I was casting with brand X and brand Y molds using a bottom pour pot, I often found it helpful to smoke the cavity. The smoke acts as an insulator and helps the molten lead stay molten for a split second longer. I now realize that the root problem was with the bottom pour pots and with the brand X and brand y molds.