I use c-clamps as well.
And yes, mix Smooth On, or any two part glue, really, really well, at room temperature. Some folks quit mixing too soon. You can warm it a little if it's a bit thick, but warming it too much can accelerate the cure. After clamping, I usually drop the entire press into my hot box that I made for glass bows. Its thermostat is set at 185 degrees. It cures faster and supposedly creates a stronger bond. But I've allowed it to cure at room temperature without an issue, so, who knows.