The paint is "bug yellow" from cloverdale paints (their code 7400201s; I /e clr bs standard tinted my-12y about $30/gallon)

Olson products, inc. Olson products, inc. P.o. Box 1043
medina, ohio 44258
(330)723-3210
make sticky stuff; 39.95/gal +$13 ups

double sticky glue
dur con manufacturing
11267 ravenscroft pl. Sidney v8l 3x9
(250)656-0392

(these folks purchase the material from olson so you may want to buy directly from the supplier but for small quantities purchases from dur con may be more economical since they purchase bulk quantities.)

Create a workspace by taping newspaper down to one's work bench.

To paint posterboard: the paint should be thinned with approximately 10% thinner (read the directions on the can or test it to make sure you're not getting thick bubbles on the cards but getting adequate coverage). Paint one side, hang the poster boards let dry for at least four hours then paint the other side. Make sure to leave yourself enough paint to be able to paint the backs of cards (i.e. when you use up half of available paint, stop!). Pour the paint in the tray back into the can and seal the can while cards are drying- if you wrap the roller in a plastic bag and put it in the freezer while the posterboard is drying you'll only have to clean it once.

Outline the 5" x 4" grid guidelines (such that one posterboard will yield 28 4"x5" cards) on one of the yellow-painted posterboards. This will become one of two glue-free, outside faces of the stack that is made when one applies glue to the painted posterboards in the following way: using a paint roller (much faster) or brush, spread glue on the face opposing that with the grid lines. Set this sheet aside. Apply glue in the same way to another sheet of posterboard and then place this sheet, glue-side down, on top of the first sheet and spread glue on the top surface. Repeat (it may be tempting to stack a fresh sheet of posterboard on top of the stack and apply glue to just the upper surface since the lower face will absorb glue from the sheet on which it is resting-- however this will create an inadequate glue coverage on the final product). Proceed until the pile is about two inches tall.    

Leave the top surface un-glued

(such that both faces of the stack are free from glue for ease- of-handling).

make sure that the sides of the sheets are aligned fairly well. Flip the stack so that the grid lines are on top. Saw the stacked posterboard on a band saw or with a jigsaw and separate immediately or your cards will form nice yellow bricks. Put the cards in the appropriate storage/carrying racks (spreading glue on the glue-free side of any cards produced from the outer-most posterboard).

Since the sawdust absorbs much of the glue from the kerfed edges, sawing the things on a bandsaw makes much less of a mess than one might think.