I don't know if that primer will stick to the silicone or inhibit it's curing. To be safe I would spray the whole thing down with a mold release that's compatible with the silicone you plan to use.
The two main silicones people generally use that I've seen are Rebound-25 (brushable platinum cured, I've been happy with it) and Moldmax-30 (I don't know much about this one, but I've heard good things regarding it's quality). Also, fiberglass mothermolds are so much more awesome than plastipaste for form fit, strength and lightweight.
This is looking really great smick!