In all my years of building and as much as I want a rocket to look good, after one or two flights they get beat up and it just isn't worth all the effort sometimes. Get it looking good. Good primer good paint and then let it be a rocket. I don't fill spirals much any more I will do some filling on fins but I don't get crazy about it. Unless that is some of the fun of it for you, by flight 3 or 4 the kinda look like crap.
Now if it is a scale model or a special occasion I will go all out (like cert 1, 2 & 3) but for a 3FN sport flyer, build it sound, paint it up and and take it to the field and let it fly.
Looks good so far.
TA