You are going to need to use a sealer first, certainly, and then a release, possibly. Platinum cure silicones (yours might be tin cure, which is likely) are very prone to cure inhibition by sulfur, which may or may not be present in your clay master. I recommend that you do a small test with your materials before you make your mold, it could save you the frustration of trying- vainly- to wash uncured silicone goop off of your model. Krylon Crystal Clear spray is commonly used as a sealer. Make sure you model is well coated and dried thoroughly, meaning days at least. As to release, with silicone it isn't always absolutely necessary, but is good insurance. Many general releases are formulated with silicone, which would actually act to bond the silicone rubber to your model, so check with your supplier to see which release is suitable for the rubber you are using. Mann 200 is safe to use, I believe, but double check that.