Can I use anything but commercially available soft plastic to make fishing lures?

Is there any DIY option? Can I melt old lures in the microwave? I want to make my own soft plastic lures at home. I have made a sealed mould (or mold) and was wondering if I could use anything DIY or cheap - I have some old SPs I'm going to be throwing out. If not, where is soft plastic available? Also how do I colour it? What kind of glitter can I add? How do I add scents?