[Norm Faustino]

A lot of self proclaimed paint pros use little more than standard prep work and reap the profit hoping that the imperfections wont show up for a while, the fact is the prep work is always the cornerstone of a concours quality paint job and to answer your question about what allows water under the paint is that if any sanding is done to the paint that exposes bare metal you MUST!! use an etching primer to prevent the occurence of delamination where the paint actully just sits there on that one spot holding on by its edges and the surrounding paint that is bound to the body the resulting gap, microscopic as it may be will allow condensation to form under the paint and lift it up, causing "bubbles" to form this condition is even more prone to happen to galvanized metal such as on the Porsche.
My Unqualified professional opinion!!