I guess the popularity of hardware store paint is because a lot of modelers don't want anything to do with learning how to spray paint, and having to buy all of the equipment and supplies needed to spray paint a small project.
Right now I need to paint a cowl, and this is the first time I needed to paint something in over 15 years. I plan on using what I can buy from the hardware store.
I had also tried the supposed brush on paint with a terrible outcome in the way the finish looked when dry..
It was mentioned to use paint intended for our particular use, but this is also not necessarily the answer either. I have read several threads on the use of Lustercoat, and the varying degrees of success that people have had with it. It seems as if the success rate is about the same as Rustolium.
I realize that there are those of you that cherish the painting part of the hobby, and then there those of us that don't give a rats azz about painting, and just want to get it over with.

Greg