That is a nice job, however I could offer advice contrary that would yield better results with less work...
I don't want to sound like a know it all, because I always seem to learn something on here!
Just a few notes, A) You are correct that laquer is easier to fix mistakes in! It's more brittle than enamel, and therefore cuts (with sand paper)quicker! Laquer for these reasons is also thinner... My old boss was so good at laying that stuff down, He'd get away w/o buffing! I've seen laquer scratch from a fingerprint tho!
B) Not necessary to sand between coats as described. If you do it w/modern base coat clear coat applications for cars, this procedure will get you in trouble in a hurry, never sand between the color and clear coat on modern automotive finish systems.
C) I realize the tank pictured is not a high end sports car! And I by no means am trying to put your work down. NICE JOB! 600 grit is to coarse for use prior buffing, use 1000 or finner! 600 to flatten a run is ok but 1000 before buffing or you'll spend more time w/ the wheel in your hand! Look at the base of the lightbulb and you can see scratches, 1000 will get rid of that!
All-in All, nice work! I can't believe you got away with sanding the color before putting down the clear, especially w/metallic color!