I didn't actually remember the image but I knew that Car Model covered all of the ICMA contests back then so I started looking thru 1972 issues and finally found it in the March 1973 issue .
I tried that cobweb paint a couple times on some slot cars and it worked pretty good , but I never could get the Swirladelic paint to work right .
Tim hope you don't mind me posting this . . . I also scanned that article for another modeler a few years ago , it explains both the cobwebbing and the Swirladelic paint .
https://public.fotki.com/TooOld/models/misc-/magazine-articles/swirladelic-paint/