Tony understood the same processes, Pete, I just think he had a different technique. I suppose, also, there is the question of what is meant by "sealer" and that's something Daron will, perhaps, enlighten us about. Tony was definitely old school, quite orthodox---curmudgeonly so. He'd started painting cars when people used long brushes instead of spray guns.
Tony spent a lot of time on prep work. His view was that good paint was only as good as the surface prepretation: the magic happened because of what was underneath the paint surface. He was scurpulous about not letting paint surfaces sit uncovered (primer is easy to sand). But the filler went on to bare metal. I think the reason he did this was to insure that the subsequent primer would be as thin as possible. His preferred method was to then let the primer sit for awhile (a few weeks, if possible) to allow the solvents to evoperate. His was not a production shop. His work was expensive and cars stayed in his shop for a long time.
Of course much has changed since then. There are new techniques and materials which are designed to reduce the hand labor involved in getting good paint. This is one reason I'm enjoying this thread. I'm going to do the surface prep, but not the paint itself, on my GTV. I think it'll be fun to apply Tony's lessons, but I'm certainly not opposed to using newer, etter techniques. Hopefully, that technology will allow a duffer like me to get a good result.