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This video isn't what I would call "technical". It has some good how-to for heat treating, but the information about spring design is almost non-existant. More of a set of guidelines for replacing existing springs, or making them stiffer or softer. If you want to make a spring of a particular length with a particular rate (resistance to compression, or spring stiffness), then you'll just have to do it by trial an error. This video did not cover the formulas involved for selecting the correct size stock to make a spring of a particular size and rate.
This video covers some good basic information and techniques for casting plastic and metal parts in RTV silicone molds. I'd recommend it for those starting out.