Using Gel Medium to Block In a Silk Screen

Just found this little tutorial in the on-line Art Trader Magazine about using gel medium to block in a silk screen.  I believe the author called it Guerilla Screen Printing.  http://www.arttradermag.com/how-to/guerrilla-screen-printing/  I'll write a follow-up on how well this works once I have tried it.  Would like to include pictures here, but don't want to infringe on a copyright.