In order to get the plasti-goop to cure properly it must get up to 290-315 F. Any hotter and it might burn. Lower and it might not fully cure. Lower takes longer, higher is much faster. I personally use a Black and Decker toaster over and just dial the temperature and watch through the window. The contemporary ovens do use a light bulb. A heat lamp might work. You could put the lamp right over the mold or put the mold on top of a bulb with a flat face like a flood light. No matter what set up you use you must follow the temperature rules stated above. You might be able to take an old cookie box tin and make a hole big enought to get a light bulb in and that way the box might help retain the heat and do a better job of cooking your goop.
I wouldn't think of Plasti-goop in the context of cross linking in plastics. I would think of plasti-goop as gelling just like Jello. The resin is suspended in a solution that is a poor solvent at room temp, but is a great solvent at high temperatures. In Plasti-goop the polymer is wrapped up in a little ball and all the microscopic balls make the Plasti-goop look milky. When the polymers melt they unravel and diffuse into a homogeneous dispersion that then looks more translucent.
Hope that helps.