To decorate, outline the cookies with a 10-second consistency using either a #2 or #3 tip in the color of your choice (make it the same color as your background color).
You can do either a circular pattern or a more weblike pattern--I did some of both. Let the outline dry for about an hour.
Reserve some of the thicker icing (10-second consistency) to make the spiders at the end--use one of the web colors for this.
Then, thin out the background icing to a 4-second consistency, as well as the icing being used for the webs all to the same consistency and put in squeeze bottles.
Then flood the cookies with the background color.
While the flood icing is still wet, use the squeeze bottles to make 3 circles of alternating colors.
Then with a toothpick, start in the center of the cookie and drag the toothpick out to the edge of the outline to make a weblike pattern.
Let dry for a few hours or overnight.
When the icing is dry on the cookie, using a #7 tip (or any other large circular tip) to pipe a circle with the thicker icing until it resembles the body of a circle.
Then using a #2 tip pipe the legs of the spider. Let the cookie sit until it is dry.