Here's how you would paint the disc pattern:
Start by painting your normal 3-color camo. Then you'll need to cut/punch three or four different sizes of discs, from about 2mm to 4mm in diameter. Next you need to cover each camouflage color seperately (and one at a time) with the discs, so they are all touching edges and cover at least 90% of the surface. Finally you spray your second color (brown on yellow, yellow on green, etc.) and then remove the disc masks. You should have a fairly random pattern (and while the model tigerman posted is quite nice, the repetitive bow-tie pattern isn't exactly correct - it looks like only one size of disc was used).
Some prefer to draw the circles on index cards and then cut out the areas between the discs. Personally I find this much harder, and it does not produce the results of the first method, resulting in a repeating pattern which is not good.
You can attach the individual discs with a small dot of vaseline, which will hold them on for painting but can be removed easily. I'd also recommend that you use index card or a similar weight material and not masking tape, because it's much harder to punch a crisp edge in tape.