I used to believe letting new guys pour fast was good practice (you know, build confidence). Watching one rush job crack three molds in a row changed my tune real quick. Slowing them down to check each seal first made a huge difference.
Totally get that now. I mean you watch someone mess up the basic steps and it just clicks, right? Speed comes way later after the muscle memory is locked in. I learned the same thing showing apprentices wire stripping. Let them go slow until the hands stop shaking, then worry about fast. Rushing the early steps costs more time fixing mistakes every single time.
Right, that "hands stop shaking" part is so true. I saw it welding, had a kid who kept rushing his bead. Made him run the same straight line over and over at half speed until his grip was steady. The moment he stopped fighting the tool, his consistency shot up.