As far as Glyptal, some of us have been "lucky" with it for decades of use. If the oil returns are addressed prior to application, and you don't glop it on, it'll work just fine. Some parts we have coated, the Glyptal could barely be cleaned off with a sand blaster. It's like any other paint project, it's all in the prepwork and some in curing. Kaase still does it, so it can't be that stupid...
https://m.youtube.com/watch?v=dIrvPfrnXjM
I have to agree with Brent. I think it looks really nice, feels good on your fingers, etc, but as far as oil control, I can't see it doing anything to change a significant quantity of returning oil in a hot engine
I would also have to agree that lots of people have been using it for a long time with success, but I recently had a set of heads in here, from a known builder who has also used it a long time, and it was not great. If fact, I didn't use the heads because of many other issues, and admittedly, the Glyptal was by no means the primary cause for sending them back... but it sure added to it
The guides and area around the springs were pretty, but it was thick enough I couldn't fit a spring cup over the guide, when I slid it over, it peeled right off the guide and sheeted/flaked off. As I was measuring installed heights, the base of the spring mike was causing damage to it as well. All I could think it the valves loading and unloading and those flakes coming apart and going through the bearings.
Certainly must have been a bum application, or maybe it needs to NOT be loaded or near moving parts, but this was done by a company that probably buys it by the tank. My thought is, how would you know? If you have a procedure and trust it, it's cool and does smooth things out a little, but I think if it was that critical for the build, I'd likely just go at the valley with a stone before machining.
In no way am I throwing stones at your beautiful builds, needless to say you do nice stuff, and no doubt you don't take shortcuts, but I see more risk than reward for the ones I do.