[BRENT in 10-uh-C]

Many urethanes are DTM, -even if not labeled on the can. Personally I think most of this has to do with how accurate of an aesthetic restoration 'one is trying to achieve. It is very easy to "over-restore" when primers are added under the topcoat. Also know that most primer/surfaces are not designed to be "bonders" like paints of a few decades ago ...but are now intended to be levelers of the surface which is being painted. Remember the thinner the mil thickness of all the paint combined will result in a more durable chip-free surface.