Im impressed. It's fibron. I'll order some salt and let it hang out in its naked glory.

I’m no expert as I’ve annealed nylon less than half dozen times, but i think the super fine grains of the flour salt powder pack more densely and provide greater resistance to movement than regular table salt. I bought it online super cheaply.

Wow, 16 hours? I suppose on a lower that might makes sense. I typically do 10 to 12 on a pistol frame. The biggest thing is not allowing it to heat or cool too quickly. I have a 1/2" thick pan in my air fryer that keeps the lower element from heating it from the bottom too quickly. I also start at 70c and go up 10c every 30 minutes until I'm at 100c. Those are just things I've tried that work and keep my parts from warping. Also good to moisture condition somewhat before assembly. Your part will be at its most brittle state right after annealing.

I remove supports after removing it from the printer. I anneal the part in my kitchen oven, with it packed in flour salt in an oven safe baking dish. The flour salt adds a ton of stability to the part during the process and buffers the temp on both the heating up and cooling down phases.