Tamiya Light Sensitive Putty Question

I recently had to enter into the world of putty to fix a rather nasty gap. I usually use Super Glue to fill in small gaps, but this one needed something more substantial. If anyone has ever tried to attach the wings of the Sruce Goose to the fuselage, you know my dilema. I looked around and decided to use the "quick" setting Tamiya Light Sensitive Putty. (The tube comes in an ominous black plastic pouch.) After it dried, I wet sanded it smooth, under running water. (I have this thing against putty dust in my house) The results were OK. The problem is, this plane requires a natural metal finish. I have seen several posts about the difficulties in covering up Squadron Putty, but not Tamiya. What primer should I use to hide/seal the putty repair?