Here is my take on the heating issue. It sounds like you are in a similar position as I am. You have not been doing this very long. If you do not have very many cavities to fill, then put about 2 oz. of plactic in a pyrex and nuke it. That pours about 5-6 5 inch stick baits from a Del mold. Once you get the hang of that, you can increase it to 4 oz, and so on. Just remember once you double the plastic you must also double the color, salt and anything else you put in. Good luck.
P.S I have a Del brush hog mold that was used only once. I do not use it any longer, any suggestions on what I can do with it? Thanks. Saint