You can melt the plastic worms and pour with them. I have made hundreds of jigs with old bass worms. The trick is melt the worms slowly in a microwave. If you try to melt them quickly the plastic will burn. I use an old low wattage microwave and have never burned any in it. Cut your worms into small pieces and put them in a Pyrex measuring cup. Microwave for 30 seconds and then stir. repeat this until they turn liquid and pour. You will learn all the tricks as you go along.

