Your technique is beautiful but I think you need to be a tad more detailed/specific when making tutorials. For example, how did you blend the colors from Picture 5 to Picture 6 and so on? That would be a little helpful.
If your tablet has pressure capability (tapering), then it should already be enabled in Paint Tool SAI (I'm assuming that's what you're using). If you're not seeing a difference, then it could be that your tablet is too old or SAI isn't picking up any pressure. Go to Others > Options, and make sure "Click detection pressure" is set to 0.