Bob,
Sorry to learn of your problems with the finish of your P-47. Alclad is an excellent product but it can go wrong with little warning.
I have read of others having problems before when using the combination of Alclad over a Tamiya base coat. Since I don't use Tamiya paints myself I can't tell you what went wrong with the Alclad on your model but I CAN tell you what I use when working with Alclad, I have had excellent results when using Model Master enamel gloss black as a base coat.
The key to using enamel gloss black is to thin it quite a bit and put on a good wet coat but at the same time not a thick coat, only put as little paint as possible on the model. Thick coats of paint do nothing to help and can work against you if you are using Alclad, a thick coat of gloss black will take a lot longer to dry and may allow more dust to get into the paint while it dries. A single coat of highly thinned gloss black paint will dry much quicker and also help avoid orange peel which is a real advantage when using Alclad Chrome or other highly relflective Alclad shades. But a word of warning...when spraying any highly thinned paint keep the airbrush moving to avoid runs, also start and stop the paint flow from the airbrush while its not aimed at the models surface.
Some people on other forums have said they had cracking problems when using enamel paint as a base coat for Alclad but I am quite sure they sprayed over a thick coat of paint that was not 100% cured, after spraying enamel gloss black be sure to let it dry for a few days to fully gas off before adding the Alclad and there should be no problems especially if you had a thin coat of gloss black.
Matrixone