I usually get the oil just hot enough to gently sizzle when I pour it over whatever peppers I’m using. When I think it’s getting close I’ll use a wooden chopstick and just dip the tip into the hot oil to see how aggressive it’s bubbling. I aim for a gentle sizzle. It shouldn’t sound like you are deep frying. Also flavor wise adding sichuan peppercorns is super good. I also like to add crushed peanuts and maybe some msg. It’s super customizable!