Like many other things, I don't think today undercoating products are same as they used to be. I know I used stuff out of a can 20 years ago that went on heavy nearly like factory.
I recently tried 2 kinds of Rustoleum spray undercoating - regular and Professional. Both covered good, but not thick like factory. I really could not tell much difference other than Pro is twice the price. If anything I thought the cheaper one had more build. I was wondering how much temperature has to do with build up. If its solid when dry it should not matter, but if it traps bubbles like spray foam, it may not build the same if its cool.
