Good job. I am partial to yellow on my arrows! I use wipe on polyurethane or spray polyurethane on my arrows. Like you I use model enamel for cresting, but have found like JAG it works better if you let them dry a day or two before you overcoat them. 2 coats of poly on shaft and let dry, then crown dip (or spray in my case), let dry, then crest, let dry for 24-48 hours, then one final coat of poly over everything.
To be honest with you, I only do this for my fancy arrows now. My hunting-practice arrows are much simpler. Stain, 3 coats of poly, yellow or white nock, 5" 3 feathers-2 yellow, one natural barred. They shoot as well or better than the fancy ones. I spend my extra time making sure they are good and straight.
Ron