Smokin, nice work!
Let you in on something. Unless you are using Alclad II "chrome" you don't need to use a black primer. I use no primer at all for the purpose of using Alclad but more for other things like checking seams and sanding work to check the finish of the work before I spray. Whether or not you primer, the key to a good NMF is to make sure the surface to be painted is as perfect as possible, including any body work. I've used Tamiya primer, Krylon Gloss black and nothing at all and have had great finishes. Infact, bare, polished plastic has worked as good as anything for me.
Now, before you discount any primer under your Alclad remember this. Alclad is a very HOT paint. If you do spray it on bare plastic go slow and mist on the first couple of coats. You can see it dry as you go. Then, after the first couple of coats you can apply a heavier coat. The paint drys so fast that you don't have to wait for the initial coats to dry because they do in about twenty seconds.
If you should decide to apply it all in one, heavy coat your plastic parts will protest very loudly and nastily. Trust me.
Now to answer your initial question, yes, you can use gloss black enamels for a primer. Make sure it's dried well though, before spraying your Alclad. A real popular paint is the afore mentioned Krylon (via Swanny) decanted into a container and sprayed through the AB. And I've heard of some folks who like to use Future as a primer. As long as the finish is shiney.