I worked for this guy for a few years in the very early 80s, I think the videos are a little hokey but there is good information to be found.
All the paint techniques apply to non custom paints as well.
Whether or not it is cheaper or not does not matter too much. This is my hobby (along with golf) and for me the journey is the enjoyment. The sense of accomplishment. I will begin by sanding down the passenger side panels and see the magnitude of the undertaking. If I do not have to replace panels, I will keep going on the prepping the car for paint. If the job gets too overwhelming, I will get professional help. There is no timetable at all to begin or to finish. I understand also that it would have been better to start with a bare shell and do the bodywork first. But, the car was not going to be a driver originally. Now that the other parts are finished I don't want to remove the drivetrain to do a proper job. The glass and exterior items will be removed but I do not want to remove the drivetrain and the interior if possible. If that is not possible,,,, UGH,,, I will face that soon enough.