I use the clamp style curling irons with porcelain in them. I am partial to Conair. I use a 1/2 inch for the bottom most layers and a 3/4 for everything else. That said I have naturally very curly and very thick hair and if I use hot rollers it refused to give up any of the curl, when I wet set it can take 12+ hours to dry and that is with some minimal drying. So heat tools are my preferred option. I also clip and or pin my hair into pin curls to allow them to cool.
Ladies, when you get a moment, look up Babyliss 2667u. It's not cheap, but the price is coming down. As I have explained before, my wife and her friend style hair at events like burlesque shows, they are also in demand, or were before covid 19, at vintage events. When one lady explained that she wanted, natural wavy tresses, then saw how my wife did them for her, instantly, the lady said: "I have so got to get myself one of those."