Hi LR,
If I understand your question correctly, you need to know what to pour the silicone into in order to get a finished mold.
Since your molds are going to be small, I would recommend using a clean, disposable plastic food container. I find the dairy product containers from the grocery store work well. Make sure you have the container and lid. Cut the bottom off of the container and make sure the lid is securely fastened to the container. Turn your container upside down and secure the model to the inside of the lid. Mix your silicone and pour into the container. Once it is cured, you can easily pull the flexible plastic away and you have your mold.
As for sealing resin, I dont think that is necessary if you use a good quality resin to begin with.
Good luck!