Snip from DT Tim:  "but I just overthink things"

I am the same way, always overthinking things. So what I do now is when I think I'm about to overthink something, I step back and think about it before I go any further. Give it try and let me know what you think. I think it helps. 

Grand job that Tim.
In future, when you fill anything , fill , then prime up first with BARRIER COTE. I have only seen it in aerosol at £14.00 a pop. 
One coat, flat back so you rub through that in places then another two coats . Quick tickle with a fine scotch pad just to clear the dust effect off, then primer over the top.
It neutralizes the chemicals in the other products .
Dolphin fine knifing putty for air holes. Nil reaction as it's like water and comes in a carton not a tin.
To get rid of orange peel easy, Rub down with 1200,2000,3000 then hit it with Feracle 2G then 3G.
Same on the top coat . 
You can measure the shine. It's like glass. 
I learned the hard way too. £300 later i finally sussed it, however, mine was two stage water based then i dropped something on the tank. As you said " Knob ed "

I wonder if any of you guys can clear something up for me, did the factory clear coat over the decals? I’ve always believed not as you can sometimes see tanks with scrapes and missing decals.
Plus, wasn’t cellulose paint used back in the day?

I’m in a discussion with my decal guy and he’s saying decals were always “lacquered “ over.

I don't think they did. I think they may have had a clear film as part of the decal though. 

That said, modern decals often say you must clearcoat over them...  they don't seem to have a clear decal layer over the top though.

Hopefully someone knows for sure.