These instructions are pretty close to how I did it.
http://www.cornholehowto.com/build-them-boards/dimensions/
I used 1/2 in carriage bolts instead of 3/8 and a better board for the top face. Home depot actually has boards that are already 2'x4', but I can't find a link. I think it was called a "handy panel" like this:
http://www.homedepot.com/Lumber-Com...202088924/h_d2/ProductDisplay?catalogId=10053
but it was 3/4" thick.
For paint, I did use a primer (another ~$10 I forgot to mention). Then I painted the whole thing maize, taped off pretty much the whole board, traced stencils I made of the parts I wanted to keep maize, cut away the appropriate tape, painted it blue, then removed the tape and put on a few coats of clear coat.
To make the stencils, I cut shapes out of paper and traced them on painter's tape to visualize them. I only did one side of the wing/top surface curve and I drew a line down the middle of the board to line up the edge of the stencil on, flip over, then do the other side. To get the curved lines, I taped 3 or 4 sheets of paper together, tied a string to a pencil and had my wife hold the string so I could draw the arc. The radius was somewhere between 6-8, but I didn't measure exactly how much it was. To get the stripe, I traced the arc on painters tape, moved it over 3" and traced it again. I marked points on the stencil where the arc intersected the back edge of the board and the other curve and measured how far these intersections were from the sides of the board so I could put the curve in the same spot on both boards. I know I'm not so great at writing instructions, but maybe I'll come back and try to explain better if people are interested and if it's not clear enough. Right now I'm supposed to be booking hotels for a wedding. I need to pack and bottle beer before we leave tomorrow.