Im sorry Michael but I have to disagree with you on this one, this time.
I am extremely particular about the construction and materials of our equipment. It would be a shame to go to all of that effort and then in the final step trim a few pennies on one of the most critical aspects; weatherization.
Heres' my method:
We shop for the best woodenware. Tight joints, few knotts, zero defects. Then we glue and crossnail the boxes in a box press.
The boxes are then primed and painted with the best stuff you can get your hands on.
And I agree with Bullseye; we use semigloss on the boxes and GLOSS on the lids and bottom boards. Years later you can hose them off and they look like new. Forget flat.
Anyway, last year we used Olympic semigloss which turned out fine if you didn't mind 3 or 4 coats. Not enough solids for my taste.
This year we are trying Behr. Goes on like yogert but one or two coats and you're good to go.
Just say NO to excuse-izm!
If my bees die, I am responsible.